After careful consideration, I bought one of the DMC Afterburners for my 05 CRF450R. After riding with it, I'm going to purchase one of there Quiet systems for my 2004 WR250F. Installation was too easy, didn't even need to rejet (I am at 2200 feet). It also came with a spark arrestor and an option to install a quiet insert. The power is VERY strong and didn't fall off. Really an impressive system!!!