Cpi's for sand and drag, or pro circuits for all around. Thats about it. I have had CPI's on mine since it was stock, and love them, but I like to ride dunes and drag some too. Friend of mine has FMF SST's and they seem to be a real good pipe also, I'm just not a fan of the toomey's.......I guess it all depends on what his future plans are for the bike... :cool: