01 Quad cab cummins with ATS tranny and torque converter. I am running the TST power max and quadzilla and both in fuel economy with intake and 4in exhaust I am right on par with others. I get 21-22 empty and 17-18 towing the land cruiser on the trailer but it isnt a car trailer it is a 26ft roll back dual tandem equipment trailer so twice+ the weight of car trailer. The biggest fuel mileage change was going to 315's with the 4.11 gears my milegage went up it doesnt like the mileage pulling over 2K RPM. I figured actual mileage instead of the liar others have spoke of.