I have a rattle, that when I go over small bumps it sounds like a mudflap/fender/exhaust vibrating , enough to drive one nuts, (thank God for the awesome stereo). Took it in twice (two diff shops) and even though they hear it no one can find the loose piece. Exhaust is tight, drilled the plastic wheel well in tight to the body with one screw (where it was a little loose) and it still makes the rattle. They say bring it back when it gets worse. It's bad enough though. Any ideas? It sounds like it comes from front passenger side under engine or near right wheel.

Thanks