I've got a Bassani stainless cat-back on my '03 GT. The cat-back has been on there since 2005; lately I've been hearing rattling coming from under the car when hitting bumps in roads and such. I decided to check around underneath to see if I could pinpoint the source of the rattle. I initially narrowed it to the exhaust, and then I'm pretty certain I heard the rattling coming from within the mufflers. So my question is, what is in these mufflers that could come loose like that? I doubt I'm hurting anything but it sure is annoying to hear the rattle so much.