Now I could be wrong but I thought we were flying by the AMA 424 rules. No modified engine under a certain $ amount. The engine of choice for years has been the Thunder Tiger pro .40. I am sure it still is. With the contest provided APC 9-6 and %15 fuel.
I have not a actually attended an official pylon event for several years but I want to try to hit most of them this year. I need to get %100 current with the rules but I thought maybe you guys might have some insight into a little better engine.