i got a 93+ tune for my mustang at American muscle. and when i first did the tune i noticed a rattling type noise and thought it was my CAI. however that is not the case. i just turn it back to stock and it does not do it. it only did the noise when the gas was down. now it is on stock and it wont do it with the pedal to the floor. i also notice my mpg dosent not change between 93 or 87 no more. the 1st time it Jump to 30 mpg. after 6 months of ratting i am at a solid 23. that including same driving habits and same amount of highway.