good question, How could I test that?
the only time I had a problem with a cat, it fell apart inside and I had to bash it around and get rid of the porcelain honeycomb stuff inside, then it was ok, but that was a different car. I'm not hearing any weird noises but the exhaust did seem to shake a bit more than normal come to think of it. It seemed to have not a rough idle but I couldn't figure out why the engine seemed to shake more at idle than normal It's idling pretty steady but a bit high , maybe 1000 RPM but it also seems to vibrate in a way that's hard to describe. sort of a droneing noise rather than a happy tick tick tick..

I think I pulled the tranny mount out and looked at it , decided it wasn't broken and put it back in. I was wondering if I had backed my tailpipe into a curb or something and maybe mashed it a bit that way. thought maybe it was hitting the body somehow.

That's not something I've considered. Thanks for the idea.