For the rattle at the rear try driving about with the rear seats folded down, if the rattle disappears it's likely the latch/hook that the seat locks into when in the upright position. I had this problem on my 2003, 3 door MP3, the dealer replaced both latches under warranty although only one was rattling. (Sounds obvious but also make sure there isn't a locking nut or something rattling around in the boot.) Good luck.