Pretty expensive way to learn something. Also a shame to ruin an engine just to see if you can make it more powerful. Funny how all the big boys who are into racing including pylon racers and C/L speed guys use tuned pipes to gain more power. Think maybe they know what they are doing?? They sure aren't chopping up their engines. Guys like Dubb Jett design their engines for max power without the need to chop on them. Most R/C engine manufacturers design their engines to be as powerful as possible while still maintaining reliability and a good idle. They have to to be competitve. So far none of you have mentioned anything about the crankshaft and venturi. Back in the days when I ran Rat Race and C/L speed that was one of the ways to get more out of an engine. It was also one of the "tech tips" Hi Johnsom put out for improving the power in a Johnson engine.