I think alot of the problems come from the metal high speed needle bracket getting hot and starting the fuel to boil before it enters the carb. You can see it in the line bubbling and boiling. OS used to have this problem as well and have switched to a composite high speed needle assy. I first noticed this problem last week with my sons plane running it in the yard to remove all the fuel from the tank. I think the non remote needle engines by GMS would solve this problem. I have stopped using the GMS engines in my planes and went to using Super Tigers and SK engines and have not had any more problems. Let me know if you notice your fuel bubbling in the lines as well.