I've got the kit with the air intake on an 02 TJ Sport. Also have cat back exhaust and header. With 31's and the 3.73 ratio mine had a lot more snap than the stock rubi for comparison. I noticed more low end torque, could do 40-50kph in 5th and accelerate out of it. Now than I have 33's I lost a bit but it's still pretty strong. With the 31's when I put it on I didn't notice a difference in mileage; with the 33's I've lost a little bit, not much. Installing it was really easy.