The FMF Desert pipe(KX15D, I believe) Is the best top end pipe out there. Whatever you do , don't try the Dynoport. I bought one of their " big volume top end" pipes and it sucks.Cost close to 400 bucks, fits like crap. The motor would not stay on the pipe under a load. The headpipe flange would only go into the cyl. to the depth of the first O-ring. I called them and they said they knew about this,and told me to gob silicone on it. I wanted to send the pipe back, but they refused to stand by it. It's too bad, because it looked great. I tried all kinds of jetting and timing with this pipe, and it still never pulled the Hill like an FMF Desert.