Moped Army

Following earlier advice, I took care of air leaks. I now have achieved 25 mph on the flats and better power on the hills. The throttle adjustment has to be turned has to be turned out several more turns than Fred's recommended 1.5-2 turns. Inside there is a throttle needle that I have set on the top groove. I was wondering what would happen if I dropped it down some and richen the mixture? Also, would I be asking for teouble if a chopped the exhaust pipe a few inches, moved the baffle back, as well as replaced air filter with fowm to allow greater intake? I would love to get the speed up to 30 if not greater. Please help!
Matt