New exhaust install, now I've got a knock
 

Ok, installed hks hipower exhaust, I've been real happy with exhaust note etc... I know theres no leaks, but it would seem starting off from a stop on occasion like when engine feels like it torques if you almost stall something exhaust wise is making contact with unerbody or something.

It sounds like directly under drivers seat, exhaust is no where near body or crossmember cat back, but the cats themselves have very low clearance... I dont quite understand how the exhaust itself could possibly cause cats to come in contact w/ body but I can see anyplace where there was going to be contact anyway, dont see any bare metal or anything.

I guess I am just curious if its a common problem or if anyone can point me in the right direction.