I have an '02 coupe MN6. Engine and exhaust are stock, except for the addition of a Borla X pipe .... and I did the 'bypass' at the rear. I recently dropped the exhaust and cover plate and insulated the tunnel for heat. The insulation works great! ..... but now I notice an exhaust resonance/vibration at ~1600 rpm when under load. It's really only noticeable in 6th gear when doing ~72 mph. It might have been present before I did the insulation, but I don't recall hearing it. Has anyone else experienced this? Is there a fix? I've thought about trying some things that might change the resonate frequency of the exhaust, but thought I would check with you experts first!! Thanks for any suggestions you may have!

Shoot .... I meant this for the C5 tech forum. Can some advise on how to move it? ( I own an 11 GS too so I sometimes get confused. ha!).

Fixed it. I was pretty sure it was the exhaust resonating at ~1600rpm. .... so I connected the two inlet pipes, just ahead of the mufflers, with a pieces of rubber hose to deaden vibration. A little crude but effective. I might 'pretty it up' sometime.