I have a 99 WR400 with stock exhaust except for a GYT insert that I bought from the Yamaha dealer. This is suppose to be less restrictive then the stock exhaust. I wanted to see if I would get much of a power gain by removing the insert but did not notice much change including the sound level. Am I missing something since I have read that running without a insert makes things really loud. Are they maybe referring to removing the whole end that requires removing the 3 bolts? I want to make my exhaust flow well so that I can get most out of my engine without getting real loud. Does the GYT insert do a reasonable job or do I need a aftermarket exhaust to make things come alive? If I really do need a aftermarket muffler/exhaust. What might you recommend that would get me a noticeable change over stock (with GYT insert) and still be on the quite side. I would appreciate anyones thoughts and experiences on this matter. I have done all the free mods and will be installing my new JD jetting kit this week. I feel that this bike rips quite well as is but do not have anything to compare it to.