I've been noticing several people posting topics about noise when in reverse. I started to hear these noises myself the other day and just finished resolving it. I jacked up the car completely and began snooping around and found out that there is a metal brace midway down the exhaust pipe(roughly right beind front seats). I noticed it before but this time it was about 1/8-1/4 inch away. I applied gentel pressure, and sure enough it was it. There are 2 bolts you need 12mm socket, an extension will help. It seems as if the hangers begin to sag...who knows. I also removed the rear right frame anchor thats next to the exhaust as well. When I installed my exhaust, I knew it was close, but not as close as it was this morning. I have a greddy evo2 exhaust and the canister is huge it was clearing by about 1/2 inch. There are 2 bolts there, you need 14mm socket, about a 10-12 inch extension with swivel head( to make it really easy.) Anyways hope this helps, just finding solutions, and preventing future need to.