I have a 02 supercrfew 5.4, dual dynomax cat backs, super chip and K&n cold air intake, and untill about 2500rpm the truck is gutless. I had 35" tires and 4.56 gears and went back to stock tires and 4.56 and the power isn't any better. Asoon as I get to 2500rpm hang on tho, cause it pulls hard. I changed the fuel filter,a nd cleaned the air and I don't know what else todo. Right now I'm at the point that I'm going to get rid of it. It has 71,000kms on it.