The TC185 and TS were almost identical other than the TC had a dual range gearing selector as they were shooting for a "trail and street" bike at the time, and idea that never really succeeded to this day. Nobody made an aftermaket exhaust that Im aware of. The stock exhaust setup was great for midrange and trail riding, and better than the high rev MX bikes of the time. In the 70's it was common to pull the signal and tail lights off and add knobbies to make them a trail machine. I would not use a clamp on filter because its location is way too vulnerable to the elements, and as I said, I doubt youll see any gains from it with the stock pipe.