[C5GTO]

Yes, old style sidepipes as they were purchased in 1992 or so. After putting up the first post, I decided to take the car for a drive to try to further diagnose the rattle. It's certainly sounds like a loose baffle with most of the noise coming in the RPM range from idle to 2,500. The rattle sounds like shaking a few ball bearings around in a tin can. Above 2,500 RPM the noise almost completely goes away until you lift the throttle and then it came back.

Well, after about 30 minutes of driving, I took a hard right hand turn and the rattle just went away. One second rattling away, the next just gone. I'm guessing the baffle somehow vibrated itself back into the hole it came out of or somehow broke loose on the other end as well. With my luck it's probably temporary and the rattle will most likely come back. I do like the new exhaust sound though as it's a bit more throaty now.

@olddog: I'm guessing the baffle you screwed down is in the middle of the muffler part of sidepipe. Can you give me a sense for where? Like how many inches behind the collector to muffler weld did you drill the hole for the screw? I just might have to try this workaround if the baffle starts rattling again.