You have two different types of power adders. Modules, or boxes as they are called, plug into your existing wireing harness. They go between specific sensors or injectors on your engine and the trucks computer and manipulate the signals that the computer is seeing, and sending back to the sensor or controller/injector. The different settings on the boxes will change the degree of manipulation of the signals causing a greater change and more power.
Programmers plug into the trucks odb port and actually reprogram the trucks computer. It physically changes the computers software to a new one provided by the manufacturer.
The more power usually comes from the addition of more fuel, higher pressure fuel,and added timing. The added timing is where most of the increase in mileage comes from. The addition of more fuel is usually when you are running it hard. Under normal driving conditions, you don't use any more fuel than you did before.
Hope the water is not quite as muddy now.
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