rattle

not sure what it could be. initially thought it was a squeak from the foam around the spare tire underneath the cargo mat. added some friction tape and determined that the sound of the foam squeaking and the creaking that i'm hearing are different. any other thoughts as to what it could be...

I'm trying to diagnose some nasty rear end rumbling, and came across the rear-most heatshield (the one with 4 bolts, above the muffler and hanging between muffler and gas tank). Two of the bolts had rust around them and the tin was rattling loose something fierce! Is it OK to remove this heat...