Question about rattle in CR sidepipe

[C5GTO]

My CR Cobra just developed a loud "rattle" that sounds like it's coming from the muffler part of the drivers side, sidepipe. It's hard to tell the exact origin given the loud nature of a running Cobra's exhaust. It sounds like a rattle (two pieces of metal banging on one another) at idle and changes sound somewhat as the RPMs go up. My guess is the sound change is because the side pipes have some shake at idle that smooths out with RPM. It's fairly loud at both idle and above.

I thought at first the sidepipe had developed an exhaust leak at the header to sidepipe flange but I've verified the gasket is still good there and bolts are tight. I thought the fat part of the sidepipe was just a glasspack, but is there some metal in it that could have become detached?

I've got about 40K miles on the car and externally the sidepipes still look great due to having them JetHot coated when new.

Has anyone had something similar happen to their CR Cobra? Any ideas? Has anyone cut open a CR sidepipe and know what's actually inside?

My inclination is to keep driving it and see if it goes away or gets worse. Good idea or bad?