heres the story for the exhaust rattle. the source of it comes from the pipe numbered 7, 8, or 9 in the picture below (depending on your model)



inside that part of the exhaust, there are several "inner" pipes that are welded on from the factory for some reason that i dont know. basically, over time, the welds come loose and it produces a rattle at certain RPMs. if you want to replace this part, its gonna cost you a few hundred dollars which is just not worth it...unless you know about the cheap way....

WHAT I DID TO FIX IT:
i went down to the local meineke and asked the guy to burn 4 holes through that piece of the header, and to fill it back up and weld it together as one piece again. he did what i told him to do, and the rattle is GONE FOR GOOD. there hasnt been any rattles for like 7 or 8 months now. IT WORKS. i will try and steal one of my friend's digital cameras and take pics of exactly what he did..remind me if i dont post them in a few days.