I recently bought '99 YZ400 with an FMF exhaust on it. Problem is it is way too loud for the woods. Has anyone fitted a WR exhaust(not header) on a YZ? I spoke to a cycle shop and the sales guy had his doubts about the bike running correctly. He mentioned the WR's different timing and cam, along with the fact that the WR exhaust is more restrictive and may hurt the YZ engine. Since I'm a thumper newbie, I need all the help I can get. Would it have any negative inpacts on the YZ engine? Would I need to re-jet? If so, what size? Let me know what you all think. Thanks guys.