Horsepower is addicting. As admitted powerhaulics we couldn't help ourselves from indulging in the latest diesel craze known as stacking boxes. Stacking boxes is actually combining an inline pressure control box and a computer performance downloader to increase engine horsepower and torque. To get a better idea how this actually works and what the real-world effects are on your truck, we guinea-pigged our 11,000-mile-old '06 Dodge 2500 5.9L Cummins with one of potentially hundreds of configurations. We started with a Predator programmer from Diablo Sport and then decided to "stack" it with an inline fuel performance module, or "box," from TS Performance.
The Predator is a handheld downloader that programs modified tunes into your truck's computer, giving you a range of horsepower options from stock to 180 hp! ("Tune" is diesel slang for different programming levels.) Once the new tunes are installed, you select one then stack it with an inline pressure box (our MP-8) that installs under the hood of your truck by connecting to your truck's MAP (manifold absolute pressure) sensor and fuel pressure sensor. The combination of the Predator and the MP-8 can result in incredible power gains at the cost of serious fuel consumption.
We decided on the Predator programmer because it recognizes whether or not the truck has an inline module and allows the module to increase fuel rail pressure instead of the program doing it itself. Using the OBD II port found beside the hood release inside our '06 Dodge 2500 Cummins, we uploaded the eight available tunes (four stacker, four nonstacker)
Once we were accustom to the program's various tunes we proceeded to dial up the MP-8 module using the control knob on the dash so we could gather individual impressions of the various levels. For testing purposes we turned the knob to full power for each run. This should give us an instant 100 hp in addition to the program's various performance tunes to let us find what is the most compatible for our diesel.
Our goal was to have a stackable setup that would increase power and economy and, with the twist of a knob, throw down that extra power for any situation whether it be Baja-ing in the desert, blasting through the mud, or pulling our junk to the trail. All smoking aside, the power difference was enough to make any grown man feel like a kid again.
The Predator from Diablo Sport allowed us to choose from a handful of programmed performance tunes on the fly and only took about 10 minutes for the one-time download. For test purposes we concentrated on four different stacker tunes: Tow, Performance, Extreme, and Extreme RKL (Road Kill Larry. Don't ask). Another option allows you to reload your vehicle's original tune, which returns the truck to stock, and a trial option allows you to hook up the Predator to another vehicle for a demo time of about five hours. | 
The idea behind stacking is that not only will your truck benefit from the new programming, but also the inline fuel pressure box will intercept those signals and produce even more power. Another advantage is the ability to turn one or both modules off, allowing your rail pressure to return to stock and conserving injectors and fuel. | 
The fuel pressure box simply connects under the hood using the factory plugs to the MAP and fuel pressure sensors. Our MP-8 module allowed us to adjust the power level with the roll of a knob. This helped us to dial in the two devices for optimal performance and gave us better control over the rail pressure. |
Tech Notes
The Predator programmer allows you to download new software updates as they become available. We were experiencing a rough idle with our '06 Dodge and used the provided cables to download a newer version of the programmer in hopes of curing our idle woes. Although we gained a few new options with the update, we were still dealing with the erratic idle. Diablo Sport assured us that an update was in the works and should be out by the time you read this. As soon as we have an answer we'll post an update on 4wheeloffroad.com.
The Results
The two most obvious results were the huge power gains and the black smoke. Unfortunately we don't believe that our stock transmission was extremely welcoming of the newfound power. We felt serious slippage in the torque converter. As for the smoke, we don't like being the freight train cruising down the California Interstate for a number of reasons, one being that we're afraid of the hippies and their future-killing hybrids and battery-powered Earthmobiles who would love nothing more than to track down our diesel and pour sugar in its tank. That said, black smoke is a sign of wasted fuel and particulate pollution, and we're cheap and eco-conscious, so black smoke's not cool. We are wasting energy and not getting the power to the ground. No, we're not saying that if you smoke a lot then you're not putting down the power, but we are saying that you're not burning all the fuel.