I have a Nelson .15 rear exhaust which is basically a three and half inch tube straight thru. The engine is designed to run full bore all the time as it has no throttle. I wish to sport fly it in a quarter midget and be able to have throttle control. Nelson says thats not possible but I know that there are people out there that can tell me how to do it. If you are one of those people I would greatly appreciate your input. Many thanks