I just purchsed a "05" YFZ 450, I heard That besides a pipe, jetting & filter a must do is to retard the timing 4 degrees. Any truth to this? Also what pipe would you recomend for best preformance and able to pass the 96 dbs[img]i/expressions/face-icon-small-confused.gif[/img]

 

Look around the forums for mentions of the "yfz cam mod" which is the retardation of the exhaust cam 1 tooth.

Lots of great info on pipes around here, Dr. D seems to be a popular and quiet option but I think it may just be a slip on. LTE pipes are quiet and others like yoshi have quiet inserts.