I have been noticing lately a rough idle after replacing my hks exhaust with a cobb exhaust. It doesn't seem to affect the way it drives. I just haven't noticed this before. Seem normal? It's a 2004 Wrx
Could be the exhaust hanger rubber bits aren't happy with being fiddled with, causing excessive shake to be transferred to the body.
Yeah, find some urethane ones. Not sure if Kartboy is still in business, but after using them I never had an issue with my HKS exhaust. They used to come in short and long as well, so you can finagle the exit of the exhaust to fit your back bumper properly.