got a new yz take off muffler from a friend , and put it on the wr , wow what a difference!!!! a tad loud but very noticable gain and weighs 7 lb, stock is 9 lb. had to use 170 main jet and turned air srew out a bit. i have another new stock yz muffler has abouut 1 hour on it, will take 100 bucks shipped for it. pm me or email at firstname.lastname@example.org. my buddy races the yz450 and got 2 new bikes this season and has fmf as a sponser so no need for the stockers.