This summer, I finally tossed that stock pipe on my 2003 KDX and added a ProCircuit Platnium II Pipe. I went with the 13/50 gear combination with renthal teeth and chain. I also put the PC spark arrestor on my bike. This pipe is a good bit louder which wasn't exactly what I wanted, but I still have the stock for quieter rides. All I can say is wow. This bike really screams now. I have nothing but good things to say about the PC2 pipe. It fit right on and ring ding dinged right away. The first ride I took after the mods was like riding a different bike. Not only did the pipe hit hard on the bottom, this thing revs out and keeps going. I would definitely recommend the Platnium 2 to anybody that's interested. I haven't ridden a gnarly or other pipes (which I'm sure affect the bike the same), but I am very pleased with my choice. Happy riding.