Hi, I would like to ask for some help calculating cone diameters and header length. I feel that this tuned pipe desing should work better than my current pipe. The engine that I am planing to make a pipe for is a Jonsered 49cc chainsaw (~220 mm^2 exhaust port area, 156 degree exhaust port angle, ~134 degree transfer port angle). Currently I am able to reach 36.5 mph @7350 rpm, but the max rpm on paper is 13000, max power 2.3 kW @9000 rpm. The pipe that I am using now is from 35cc mini bike, it is definitely too small and the header is too short. Could anybody suggest what desing should I use?