my exhaust has benn vibrating maybe six months after i installed it in.Connections are fine nothing is loose. I can feel some type of cabin noyse when the ac is on from the exhost.and its not the sheald from cats. I any one had the same problem please give some feedback.

 

I had this problem on my old V6 mustang. turns out my pipes got twisted a bit at the connectors in the back and were tapping the rear axle, I could hear it when i hit bumps, or really got on it.