I have an FMF powercore IV that was on my '99 wr400 when I bought it. The bike only had about 300 miles on it so the pipe had very little use. I mostly ride trails so I went back to the stock pipe with a vortec plug on the end for a very quiet solution. I thought I would keep the FMF for the dunes if I wanted to have a little more power but I has just been sitting around in my garage for the last year collecting dust. If anyone is interested I would be willing to sell it for a good price.