2003 Yukon Exhaust Vibration/Harmonics???

Anyone have any issues with an exhaust vibration? I am told by my dealer that it is some sort of harmonics in the exhaust system. It was happening at idle when in gear, they added some weights to the exhaust system. Now it vibrates at acceleration and deceleration. It's going back into the shop on Wednesday for the fourth time.

Thanks!

Yes I get it from time to time in my 2001, but I usually ignore it.

I have the same issue with my 03 Yukon XL, did you ever fid the right fix. I know this post is from 04, but can really use advice from someone that has gone threw it. Thanks