i've been told not to waste time on the gas additives. but i don't think they'd hurt. check what others say, though, first.
also, be sure if your avanti is new not to run it too fast during the breakin period. keep it steady for a while.
cleaning the carb is easy ... it takes me about 5 mins tops (from start to riding again). it can be done w/ a pocket knife, the dellorto is so simple.
what speed kit are yuo getting? be careful w/ the 70cc and even 60cc kits ... i've heard too many bad reviews. but a larger carb, manifold, and performane exhaust should get you around 40+ mph. i have a 15.15 carb, 14mm carb, and polini exhaust and my bianchi does at least 40mph. oh, i also have an 11-tooth sprocket.