Sounds like a fuel delivery problem to me also. I would check my fuel lines, tank, clunk, and make sure my tank was wrapped with foam REALLY well to prevent vibration induced foaming during flight, before I started messing with the engine. I had the same problem on a couple of flights after I installed my Evo, and foaming was the problem. I've got an EVO .46 on my LT40, and it runs better than any engine I have ever used in the .46 class.