I'm buying a pro-circuit type 496 exhaust off a yz450 but it doesn't have a header, I found a fmf header from a guy who says it came off a 426, does anyone know if this will work fine? Other than usual rejetting? My other question is are the YZ headers a little fatter than the WR? FMF probably makes both? How would I know the header came off a YZ or a WR? Or should I not worry about it? I allready have my old WR header, if it won't make a difference I can just use that with the pro-circuit exhaust and middle.