What carb? Regardless piliot that big on a stock motor will be loading up like crazy. Thats where your are getting the dying feeling at first, then it takes off. Fix the exhaust leak, and throw in a 42 piliot, and you should be good to go. In illinois, my cousins quad is running a 40 piliot, ansd a 142 main @ 70degrees, and his plug and piston wash is spot on. Elevation should be about the same, give or take 100ft. He is running what sounds to be close to the same set up.