The real difference on the Duramax L5P is not just added fuel. A simple inline box that only manipulates rail pressure can make more heat, more soot, and more backpressure because it has no way to add the right air, watch exhaust temperature, or manage what the transmission is doing. That is how you end up with harder regens, reduced power under load, and ugly shift behavior. Our Banks Derringer Tuner takes a different approach. It communicates through OBD-II and uses live vehicle data like throttle position, EGT, boost, and transmission behavior to adjust power in real time. That lets us add power where the truck can use it, control delivery during shifts, and stay inside the engine and transmission’s real limits instead of pushing fuel blindly. If a fault or power interruption happens, ActiveSafety returns the truck to stock behavior so you keep control instead of getting hit with a dangerous power loss. On this L5P, that is why the smarter tuner is the one that actually talks to the truck.
From Banks Power's race shop and engineering department in Azusa, California, the video introduces the Derringer for the Duramax L5P as the newest member of Banks' inline tuner family. According to J. Tillis, development on the L5P program began almost three years before the engine was available in a pickup. Banks had already been working with the platform in military applications, including the Joint Light Tactical Vehicle, where more than 1,000 L5P-based systems had been outfitted. That early access is presented as a major reason Banks claims deep familiarity with the engine and its controls.
The discussion is framed around a comparison with several competing inline tuning products that are frequently mentioned online: Dr. Performance, Stealth, AG Diesel, and the aFe Scorcher. Gale Banks joins the segment to evaluate how those products are built, what signals they actually use, how they behave on the dyno, and how they compare with the Derringer in both performance and safety.
The first product examined is Dr. Performance, which the presenters describe as the lowest-performing unit in the group and also one of the most expensive, at roughly $700. Banks notes that when they ordered the Stealth unit, it arrived in packaging labeled Dr. Performance, suggesting the two are effectively the same product from the same company.
After opening the enclosure, Gale Banks focuses on the simplicity of the electronics. He says Banks performed a cost analysis and estimated only $3.21 worth of electronics inside, including a microprocessor costing about $0.98. In his telling, the enclosure itself costs more than the electronics, at over $7. The technical criticism is that there is very little circuitry and very little actual control strategy present.
Functionally, the unit plugs inline with the fuel-rail pressure sensor and appears to do nothing beyond altering that signal. During testing, it was found to have a four-position switch, but all four positions reportedly produced the same power. Banks says their own testing and checks with outside contacts produced essentially the same result: negligible variation between settings and very limited overall gain.
The next step up, in Banks' view, is AG Diesel's module. It is still described as a rail-pressure-only tuner, meaning it adds fuel without coordinating additional airflow. Gale Banks argues that this approach is fundamentally limited on an emissions-equipped diesel because the diesel particulate filter has finite soot capacity. If extra fuel is added without corresponding air, the engine runs richer, soot output rises, and the DPF loads more quickly.
To explain the point, Banks uses an L5P Duramax engine on display and identifies the rail-pressure sensor connection at the front of the engine. He rejects the claim that a tuner connected only through a sensor lead is somehow communicating with the ECU in any meaningful way. In his explanation, true ECU communication would require the diagnostic or OBD connection, not a simple inline sensor intercept.
His broader argument is that fuel-only boxes increase exhaust gas temperature and soot production. Even if visible smoke is limited by the emissions system, the soot still accumulates in the DPF, causing more frequent regeneration and higher average exhaust backpressure between regens. That, he says, hurts fuel economy in two ways: by overfueling during throttle application and by increasing backpressure as the filter loads. In short, the tuner may add some power, but it does so by pushing the engine richer, hotter, and dirtier without any airflow strategy to support it.
Banks then explains why these fuel-only strategies run into the factory exhaust gas temperature protections. He states that the stock ECU limits EGT to roughly 1,450 to 1,460 degrees so the turbocharger can survive for hundreds of thousands of miles. On the L5P, the temperature is inferred from the EGR recirculation passage and is available through OBD data. Banks displays that value on the iDash as DGT.
Once a tuner drives fueling high enough to reach that temperature limit, the stock ECU begins removing fuel to hold temperature in check. A rail-pressure-only box cannot respond intelligently because it cannot lean the mixture back out or command more boost to offset the added fuel. As a result, Banks says these modules hit the EGT ceiling quickly during hard, sustained pulls, exactly the kind of use heavy-duty truck owners care about most.
He also disputes competitor claims about making power below 2,150 rpm. Using acceleration examples and shift behavior, he argues that in wide-open-throttle operation the truck passes through the low-rpm torque peak almost instantly. From idle to 2,000 rpm takes only a little over a second, and during upshifts the engine typically drops back to around 2,300 rpm, not down to the 1,600-rpm torque peak. Even under lugging conditions, he says the transmission backshifts around 2,150 rpm. For that reason, Banks considers sub-2,150-rpm power claims largely irrelevant in real chassis-dyno testing and real acceleration.
The aFe Scorcher is presented as more sophisticated than the rail-pressure-only boxes because it also taps into manifold pressure through the MAP sensor. On the L5P, that sensor is not immediately visible; Banks explains that it sits behind the throttle body in the inlet casting that the shop informally calls the "sad giraffe" because of its shape. Accessing the sensor requires removing the throttle body.
With rail pressure and MAP input, the aFe unit can at least recognize boost pressure, and its phone app can display that value. However, Banks argues that this still falls far short of a true integrated control strategy because the module is not connected to the OBD-II port. Without that connection, it cannot see the broader set of operating data available from the truck, such as throttle position, transmission behavior, temperature protections, altitude compensation, and other ECU-managed parameters.
That limitation matters, he says, because a fixed calibration cannot adapt properly to changing conditions. At high altitude, for example, the module has no broader context for how the engine should be managed. Likewise, during aggressive acceleration through first and second gear, it may overfuel and overtorque the transmission without understanding the consequences. Banks says that when this happens, the ECU intervenes aggressively, reducing power in ways the tuner cannot anticipate or correct.
Banks says the company invested more than 1,000 hours of dyno time evaluating these products. The resulting comparison focuses on measured rear-wheel output versus advertised gains.
For Dr. Performance, the claimed gain is 100 horsepower, but Banks reports only about 11 horsepower peak-to-peak, with a best observed gain of 14 horsepower. Torque tells a similar story: with stock torque at 852 lb-ft, Dr. Performance reached 877 lb-ft, a gain of 25 lb-ft peak-to-peak and 30 lb-ft best, versus a claimed 120 lb-ft.
AG Diesel's results are also criticized. On level one, Banks says the truck made 399 horsepower, which is 4 horsepower less than stock, and he attributes that to the module commanding 50 bar less rail pressure than stock. On its highest setting, AG reportedly reached 436 horsepower, a gain of 33 horsepower over stock, with a best gain of 33. Torque rose from the stock 852 lb-ft to 914 lb-ft, a gain of 61 lb-ft peak-to-peak and 79 lb-ft best. Banks argues that the advertised numbers look larger partly because the lower settings begin below stock output.
The aFe Scorcher, which does add some air, performed better than the fuel-only boxes but still fell short of its claims. Banks reports 441 horsepower, or 38 horsepower over stock, with a best gain of 45 horsepower, versus a claimed 60. Torque reached 924 lb-ft, a gain of 72 lb-ft peak-to-peak and 88 lb-ft best, again below the claimed 120 lb-ft.
By contrast, Banks says the Derringer produced 463 horsepower, representing a 60 horsepower peak-to-peak gain and a 61 horsepower best gain. Starting from a stock 445 horsepower baseline, that yields a 505-horsepower engine. Torque reached 939 lb-ft, which Banks describes as a 91 lb-ft peak-to-peak gain and a 112 lb-ft best gain, bringing the combination to 1,001 lb-ft. He attributes that result to the Derringer's ability to monitor far more data through the OBD connection, including throttle position, EGT, MAP, rail pressure, and transmission slip.
One of the most detailed criticisms is aimed at the aFe Scorcher's behavior during acceleration. Gale Banks describes a test drive in which the truck initially pulled hard off the line, then seemed to soften in second gear and become especially vague during the next shift. He says the sensation was severe enough that he initially thought the transmission had been damaged.
Using iDash data logging and reviewing the SD card on a PC, Banks examined engine speed and vehicle speed traces. The logged data showed transmission slip: engine rpm rose above the stock trace while vehicle speed did not increase proportionally. In his explanation, the ECU responded by pulling timing, fuel, and boost. During the 2-3 shift, he says the truck experienced a power loss of more than 170 horsepower. That is why the truck felt as though it had "laid down" during the shift even though the throttle remained open.
Banks presents this as a key distinction between simply commanding more fuel and actually calibrating within the limits of the transmission and the rest of the powertrain. His claim is that the Derringer avoids this behavior because it can see and respond to transmission-related data rather than blindly adding output.
The video then moves to active safety testing by intentionally cutting power to each tuner during a simulated highway pass while towing on the dyno. With the AG box installed, the truck is accelerated at full throttle and the module is switched off mid-pass. The result is immediate and dramatic: the truck loses power, slows sharply despite full throttle, and displays a reduced-engine-power condition. Vehicle speed falls into the 30 mph range, and a fuel-rail-pressure fault code is recorded.
The same test is repeated with the Stealth box, with similarly poor results. Again, cutting power to the module during a pass causes the truck to lose power abruptly and enter a reduced-power state, with another fuel-rail-pressure code stored. Banks characterizes this as dangerous because the failure occurs during a maneuver where the driver expects continued acceleration.
The aFe Scorcher behaves somewhat differently but still fails the safety test in Banks' view. When power to the module is cut during a pass, the event is described as violent. The truck again reports reduced engine power, and multiple codes are logged, including a manifold absolute pressure code and a fuel-rail-pressure code. Banks' conclusion is that none of the three competing boxes provides active safety if the electronics fail or lose power.
Finally, the same test is performed with the Derringer. During a full-throttle pass, power to the Derringer is cut, yet the truck continues to accelerate. The iDash indicates that the Derringer has lost power, but the vehicle remains drivable, no abrupt derate occurs, and no fault codes are stored. Banks presents this as evidence of active safety designed to protect the occupants and preserve normal vehicle operation even if the tuner itself loses power.
The recap closes with Banks summarizing the Derringer's design philosophy. Rather than chasing unrealistic numbers or overfueling the engine, he says the system is calibrated around the actual capabilities of the truck, the transmission, the emissions system, and the operating situation. That includes adapting to load, temperature, and other changing conditions while avoiding excessive EGT and other forms of overstress.
His central argument is that the Derringer's OBD-based awareness allows it to optimize performance within the truck's real limits, whereas the competing inline boxes operate with too little information and too little control authority. In this comparison, Banks claims the Derringer delivers the strongest measured gains, avoids the transmission and drivability problems seen in some competitors, and maintains safe behavior if the module loses power. The final takeaway is that the product was engineered not simply to add fuel, but to work with the truck's full control system in a way the simpler inline boxes cannot.