So I use to have a greddy evo 2 exhaust and I never had any problems with rattling. It fit perfectly, I put on a Cobb exhaust today and everything went smooth but I notice my whole inside cabin vibrates when the car idles and when my rpm is around 1200-1700. It also rattles under the car when it's idling, the rattle goes away while im driving. Anybody with the Cobb exhaust know what the problem might be? Im pretty sure I installed it right.

 

exhaust leak? When I used to have one it would be loud as crap. Or it could be the downpipe hitting the front cross member.

 

I doubt it's the downpipe since I didn't touch that area.

 

then exhaust leak?

 

i have the same problem but mine is stock..... time for upgrade (: