I've had an annoying rattle in my '08 for several months. Sounds like it comes from drivers side back by the axle. Been in the trunk with someone else driving, tried several things. Plastic spacers between the bumper cover and body where it mounts. Checking exhaust pipe clearances. digging rocks out of various places. New control arm bushings.(which stopped some squeaking, but not the rattle) It is frustrating to say the least. The only thing that stopped it for a little while was going through a car wash that had really good underbody wash cannons. Makes me wonder about the brake pads now. I'm so tired of doing stuff, and thinking, "Oh, that had to be it." Then discovering the dad blamed thing is STILL there.