I have been trying out different exhaust set-ups to balance out sound vs performance on my TE510. I have decided that the Husky dB killer is way too restrictive, so I took advantage of the FMF sales deal and ordered an FMF Q4 exhaust. I have a cheap Scosche dB meter so I decided to do some unscientific sound testing following the USFS standard ( open area, 20" from exhaust tip at a 45 degree angle) and the various configurations of the Arrow and the FMF exhaust. Here are the pseudo scientific results It's hard to get a steady 6500 RPM since the bike gets in the power-band and takes off): OEM Arrow uncorked 1- Idle 98dB 2- 6500 rpm 110dB 3- Peak 130dB OEM Arrow w/ dB Killer The holes on the end of this thing are 10mm in diameter, think dime size! 1- Idle 86dB 2- 6500 rpm 96dB 3- Peak 103dB OEM Arrow w/ OEM spark arrestor 1- Idle 93dB 2- 6500 rpm 103dB 3- Peak 110dB OEM FMF Q4 uncorked 1- Idle 95dB 2- 6500 rpm 104dB 3- Peak 113dB OEM FMF Q4 w/ OEM spark arrestor 1- Idle 92dB 2- 6500 rpm 102dB 3- Peak 110dB The bottom line is that the Husky is just a loud bike. It also make a significant amount of intake noise. According to my highly calibrated butt dyno the open Arrow felt the fastest on the top, but was a bit less torquey on the bottom, the Husky dB killer was nice and relatively quiet, but significantly choked up the bike and the FMF Q4 w/ spark arrestor was the best compromise of sound muffling and performance. It also felt like it added a bit of torque to the bottom end, while loosing a bit of top end. I'll add pictures and some video clips when I get a chance. Here are the numbers side-by-side: Note: even though the Arrow and the FMF have similar numbers w/ the spark arrestor in I personally think the FMF does not sound as loud since the tone of the muffler is a bit lower. The Arrow still has a bit of raspy, tinniness to it that makes it seem more offensive to the hear. I understand this is purely subjective though.