For what it's worth, I just put on the new Rinehart 4" slip on pipes and love them. Very nice deep rumble and I can still hear my stock stereo. They look and sound great. I don't know if I would want to ride behind me, but for the rider they are great. I would never leave stock pipes on a scooter. Run way too hot and are way too mellow for me. At 2200 RPM's they keep that rumble,,,, I love em.