I'm guessing most people who have added performance parts to their engine did it to compensate for things like armor, bigger/heavier tires, etc. I don't really know if you're gonna find anyone on here who bought their truck to buy "go fast" mods to actually make it quicker/faster... I have a cat back exhaust and will add a CAI in the near future, but like I said, it's just to gain some giddy up and gas mileage back from putting mud terrain tires, sliders, a rack, and so forth on it... Just my opinion though.