Bought my new audi the other day, but i want to replace the back box reason im getting this rattling noise when i quickly put my foot down on gas then release it. does this at like 5mph in 2nd gear. So i thought problem might go away if i just replace the whole back box cause i have no idea what the problem could be. Maybe Heatshield? Dont know. It will be going into garage on tuesday but if it comes out still making noise think i will just try a new back box. But whats the next best back box to put on an audi a3 3.2 i like that deep sort of sound when you slam your foot to the floor.