I have run a big gun for about 2 years. Fits with slight mods better than stock. Had to repack it after a month or so, that cost another 80.00. At idle it is quiet, fmfs are a lot louder at idle, Big gun is a lot louder at wot than fmf. As far as power gain I didn't notice anything with the exhaust alone. Here is what I run, and yes very noticable gains, I can smoke the stock tw's off the line and hang almost exactly at top end, but if we accelerate together there is no catching me. Big gun ttr 225, wiseco high compression 1mm over, web cam tw grind, 42 pilot turned all the way in, 120 main with a very small shim on old style carb. Bike runs better than stock at all elevations and from about 50 to 90 degrees. But it took me 3 years of playing to get it there. Most noticable mod was webcam, did that last with some fine carb tuning and it all came together.