I use a 9mm carb on mine with an 086 pipe, I tried 11 different pipes and this one worked the best for me. I also just bought a new 28RR Axial and my God you want to talk about top end, its got it. On the carb situation, ive replaced all the stock orings in my axial carbs and they are fine, the stock orings leak and you will have problems but if you put a good set of orings in them, seems to be just fine and I have no tuning problems until the top end starts to wear out or the front bearing is leaking.