In the good old days of carbureted engines, camshafts were con-sidered the "computers" which primarily governed engine operations via intake and exhaust timing events, as well as spark management. That's still true today, but the advent of electronic fuel injection and increasing EPA mandates for cleaner burning engines has changed things a bit.
As its name implies, electronic fuel injection requires an electronic computer to regulate injector function. But there's more to it than simply telling a series of injectors when to shoot fuel into the intake manifold. In an effort to maximize fuel economy, reduce harmful exhaust gas emissions, and still maintain peak horsepower and torque performance, your EFI truck's computer module monitors a wide array of engine systems and functions, such as coolant temperature, throttle position, rpm, exhaust emissions, manifold vacuum, air temperature, air:fuel ratio, engine load, and so on. The computer also weighs these factors against the octane level of fuel availability-primarily 87 octane-to achieve the best all-around performance and emissions standards.
There are, however, a couple of problems with this approach from a performance enthusiast's standpoint. For starters, the stock computer is something of a fence-sitter by design. In order to maintain low exhaust gas emissions, the computer adjusts spark advance and air:fuel ratios to achieve the "cleanest burn" possible while still maintaining good power output. In doing so, it does not allow the engine to work at full horsepower and torque output potential. In other words, the computer prevents your truck's engine from producing as much power as it potentially could in order to keep emissions at an acceptable level.
The second problem is encountered when you attempt to modify the engine and related systems with aftermarket performance parts. Opening up the intake and exhaust side of your truck's engine theoretically increases power output by improving air flow and combustion efficiency. Such modifications can also have the effect, in varying degrees, of increasing fuel consumption and exhaust emissions. The stock computer doesn't understand these modifications and, frankly, doesn't care. It is working within a set of parameters designed to find the ideal balance between power output, fuel consumption, and exhaust emissions, and by golly, that's exactly what it's going to do. In essence, you give your truck's engine marching orders by way of select modifications, and the stock computer wants to countermand those orders. The end result is that, like the stock engine, you may never see the full potential gains of aftermarket modifications if that OEM computer has anything to say about it.
Fortunately, there is an easy solution to this dilemma. A few aftermarket companies now specialize in increasing engine power output by way of the keyboard instead of the wrench. Companies like Hypertech, Jet Performance, Mopar Performance Parts, and a host of smaller companies all make specially designed computer modules, or chips, which give your truck's stock computer new parameters to work with. The final result is that these aftermarket chips allow your engine to expand its horsepower and torque output.