Strange rattle in back of '01 986S

[heymanwatchthis]

Strange rattling noise in back of 986S when engaging and disengaging clutch. Sounds like sheet metal pieces hitting each other, and the rattle is random. Sometimes is more distinct than others. Have done a lot of searching and listened to many rattles, this is one I have not run across yet.

Can be heard at :07, :10, :20 and :22 in this clip - Box exhaust - YouTube

Heat shields are tight and everything else under car seems to be bolted up. Inside of cats rattle some when I strike with a mallet. Does not follow RPM, sounds like a loose sheet metal part banging around - however it should be noted that I do not hear it at higher revs and speeds. My theory is something loose in exhaust.

Any ideas?

Thanks,

Gary