I had a 2005 YZF450 (steel frame) exhaust with the internals of a FMF q pipe (the fmf fell apart because it was poor quality, I used the baffles from the fmf and put them in the YZF450 exhaust) on my 04 WR450. I recently bought a 2007 WR450 so I modifed the exhaust to fit. It is pretty easy if you have workshop skills so I thought i would write a quick how to so other people can do it. Basicly you need to remove the exhaust mount that which would attach near the foot rest (i grinded it off using a dremel). Cut about 1 inch off the length off the front pipe where it joins the rear section. Everything fits now so bolt it all on and mark there the mount you removed needs to go that you removed earlier then weld it on and your done. Dont blame me if you start chopping stuff up and it doesnt work! As i said someone with good workshop skills should find this fairly easy but its not a job for everyone.