I know there are many threads on jetting but I was wondering what you guys think jetting might be if I have the AP Mod done to my carb and I live in Florida. I noticed recently it has a bit of a backfire. I noticed the screw that goes into the carb that holds the idle screw bracket to the carb is missing I don't know if this has anything to do with the backfiring but it was the only time I noticed it. So maybe if I replace that screw it might go away but I doubt it. I will keep my eye on it and see if its still backfiring after i replace it. I think I read that backfiring is caused from a lean condition, perhaps this is whats going on with mine. Correct me if I am wrong. Is jetting these things any harder than tearing apart a 2 stroke carb to jet it? This is my first dance with a 4 stroke.