Ok, I bought "Tuning Module" by Power Pro Tuning, for my 08, 4x4 4.0L
they claim more hp. when installed. It works by sending a modified signal through the factory "IAT" sensor. (Intake Air Temp) which is directly interfaced with the "ECM" ( Engine Control Module) and controls the fuel timing, fuel injection pulse duration. The signal outputted by the "Tuning Module" alters the signals sent to the computer and the reprograms itself for a more efficient tune. It sounds good I think, not sure. I'm getting a 3" lift package by Pro Comp. with new 17" rims and 33" tires and figure I might need a little more hp. If this is not the way to go, then I will get my money back.