I am a new wr450 owner. I bought a 04 model (2800.00 what a steal)and it had a FMF power sore on it . The power hit harder and the pipe was alot louder than stock. I put the stock pipe back on and sold the FMF on ebay. I like the way the power came on (less of a hit) with the stock pipe. I don't know why anyone would need more power. These 450s are very fast. I have raced quads with built CRF450r motors and built YFZ450s but I don't know why you need more power on the bikes. I love the wr450 and would say that it is the best bike I have ever owned. It is a great woods bike and is fun on the MX track.