I think the FMF Q4 is around 95 db and im pretty sure they make a quiet core insert for it as well. From what ive heard on here, its even quieter with the header, but i cant say for sure.
I really like the sound of the Q4, and it had a noticeable increase in power
trail toy: '09 700xx: trailtech vapor, trailtech X bars, trailtech riser, OURY grips, l8ton 9/16" XL swaybar, CCP Stabilizer, 23" Razr front,24" bearclaws rear, fmf q4 slip-on, EHS programmer, EHS lid, powermadd handguards, Honda Racing skids, PRM 6 pack rack, 6000k HID's
lake toy: 98 Kawasaki ZXI 1100 jet ski, mostly stock
big toy: 2011 GMC 2500 duramax CCLB 4x4, a few mods but mostly stock