I have a 2003 1500 Quad Cab Hemi with 17" wheels. I first put the Gibson Super Truck exhaust and love the sound. I had to cut about 3" of the exhaust pipe and deburr the inside of the muffler to get the exhaust to sit where I wanted it to fit. I then upgraded the computer with the Hypertech. Stiffer shifts, increase in rpm shift points, higher mph, better performance and increase in mpg. I have manually shifted my truck at 6,000 and when shifting to second there is no hesitation, and fastest I have had it is 115 mph. The third thing I did was install the PowerAid throttle body spacer and can feel the improvement. If you look around the Hypertech maybe still available for $359. I was getting 17.5 mpg driving about 64 miles at an average of 55 mph and having to stop and go about 10 times. I have driven the truck with the above improvements with some city and highway driving and still getting 16.1 mpg so highway is probably a lot better than 17.5.