The actual cats are the only thing in my exhaust that's still stock because I didn't want to have to deal with them yet. I removed the back cats (the ones AFTER the o2 sensor) and everything is 2.5" all the way through the exhaust and I think it sounds great, but not that loud. Since that's what I was going for, I was happy with it. I'd be interested in hearing how yours sounds after you're done!
2013 Scion FR-S
- current DD, after life circumstances made me get out of a Camaro
2014 Camaro 1LT
, Red Rock Metallic, wife's car once we could get a Camaro again