A while back I bought one of the new AHP Stage 3 engines, big mistake! It lasted for a few hours of riding and part of a race before the tranny let go! I was pretty bummed. After a few emails, Mark agreed to send me one of his new Stage 4 engines. I wasn't to excited about this as I did not trust his product, I wanted my money back. After I got the Stage 4, I tried to sell it to no avail. I put it in my bike and was pleasantly suprised, it made really nice power! I took it to it's first race Sunday and was clearly one of the faster bikes in the 10" AM class. To bad the tranny started jumping teeth in second and third gear before the end of the first moto! By the end of the second moto it was so bad I barley finished the race. I guess I will have to see how this unfolds, I want my money back....