Went from stock with the GYTR insert to the FMF and noticed a difference right away. It was running lean so I changed the map. Ran into a ranger so I asked them to do a dB test. I had to know. They have a chart they follow for rpm. For this bike the test is done at 4500 rpm. At 3500 rpm and the supplied spark arrestor installed it tested at 97.5 dB. The legal limit for Ca state parks and Forrest is 96 dB. The ranger said they do not ticket for a couple dB over but if you run into a prick or piss one off they can. It sounds great. The FMF is a few inches shorter and considerably lighter. The fit was spot on. The only thing I didn't like was the pipe doesn't clamp on like the stock pipe did. The directions tell you to use high temp silicone at the connection. Come on FMF, you can do better than that. M.