This was the first modification that I added to my then stock 4.0. I was sceptical of performance results when I ordered it but was very surprised! The intake which includes a polished intake tube, heat shield, dry filter, throttle body spacer, breather tube, and various clamps, made a noticeable power increase. I cannot say exact numbers for sure but it was very close if not more than the 10HP 12FT.LBS. that Rugged Ridge boasts! Fuel mileage also recieved a 2-4mpg increase depending on how hard the wyoming wind is blowing. Definatley a 5 star product!!