Now for a serious post. Have you checked your heat shields above the exhaust. I've had mine break loose when I bottomed out over a ditch, but it makes more of a rattling noise as it vibrates against the muffler.
Hatch Nation #13 : Rally Revolution #13 : ROTM Jan '13
It's Bryan, not Brian
RSVT-170 Build in Progress
Derusting Rusty Build in Progress