Rattle...

Is anyone else experiencing rattles from the rear-end (perhaps muffler/exhaust)? I've been having issues for about a week now and after 3 trips to the dealer, they still haven't been able to diagnose it. It seems to happen after the car has run for a bit (after about 10 minutes of highway driving) and I guess they don't really want to drive it that long. I talked to my service advisor, who is really cool, and we'll go for a test drive on thursday but between now and then, has anyone had this issue? I know I'm not crazy, as many other people have heard what I'm hearing. It just has to run for a while before it comes out. And for the record, my 06 has exhibited the radio skipping, a dashboard rattle, and the gas tank filling problem. They have all been fixed but since they replaced the gas tank, this rattle has been there. I'm not picky either as there are a few more dashboard rattles (including a sound that I characterize as a busy hard disk drive) that I am not even concerned about or want fixed as I can live with those.