RMS do good reliable work. Most (all?) of their mufflers are made by Butler.
I chose RMS partly for their venturi and splitter design. My impression after RMS did my TBE was performance more than I expected, workmanship good, price very competitive, noise not too bad except for droning in the cabin at mid range engine revs, they said it was due to my special twin tip request. If I was doing it again I would go for the Magnaflow, US made and pricey but VG workmanship. I’m interested in people’s opinions on the Japanese mufflers, and how to reduce droning, I put in dynamat and an extra muffler instead of the resonator.