All bikes that I have done, I have put a Dyno Jet kit in as well as some type of HMF Pipe. I think they go hand in hand with tuning. The oversize jet somehow needs to be compensated by the amount of exhaust going out. If that makes sense.. A friend just changed the main jet and not the rest ( spring, needle jet,..ect ) and we could not tune this thing for the life of us. Once he changed these things, It ran like a champ.