Personally I like the FMF on the yz's. Especially the 05 125. That specific bike is harder to jet the PC pipe! I had to go up I think 4 sizes on the main. I know one bike that roached a top end by not having a large enough main with that pipe.
Fmf factory fatty, pro circuit r304... Awesome combo. That's what David Villumen used to run on his factory YZ's. I ran it on my cr 250 and it sounded mean
