You might have bit trouble getting it to perform super well, oh the hours I have been sitting and reading about expansion chambers. Might I add it's so easy to calculate ~ max power for particular pipe is if you have a degree wheel and measuring tape. No I don't think you need a better variator, just modify the stock one. If you want more torque and something that won't burn up the motor so quick remember a longer pipe is better then a shorter pipe. Also look at pipes that have smaller dwell(belly or midpoint on the pipe) and longer cones. RPM's will eventually kill your motor, it's just more wear and tear. My 2 cents.. oh and Eric I'm going to be doing the same project :-) sounds like you will beat me to it.. I was even thinking of using a phva carb.