Not sure, I haven't heard much gain out of a pipe. You can clean up some of the welds on the inside of the Y-pipe. Reeds would be next, now many miles are on it? I rebuilt my motor along with a little portwork and a shaved head, flat out woke the sled up! I'm running RKT's dual ring piston only kit, some port work, and had my buddy with a machine shop knock a few thousands off the head to get the compression back up. Could also look at just getting it to work better, the 01's suffered from a bad attack angle, do a skid setback and run a bigger track if you can! I'm running Pilot 6.9 skis on my 01' and they really helped the sled go through the softer snow, and alot less darting! I have bar risers on mine, because I'm 6'3", may help you. I just got done completely rebuilding mine, I love the zx platform, rode a rev, its a great platform but its not comfortable for me, I'll be riding mine for a while longer!