[expavr]

"The pump boiling is more difficult to over come. It looks like I may have finally have a sure solution but it requires installing a return line which a lot of people won't want to do. I never had any problems either until this stuff came along."

GM - I think you are on the right track with your fuel return VL2 theory.

I ran into a similar vapor lock condition with a hi-performance engine. The original fuel delivery system was set up to deliver 6-13 psi thru a boost referenced fuel regulator near the carb. Under load with all the engine heat the engine would periodically starve for fuel and quit. After much head scratching, some research, and tinkering I discovered that "deadheading" the fuel delivery at the carb created a situation where the heat buildup in the fuel delivery process caused the fuel to vaporize somewhere between the fuel pump, the fuel regulator and the carb. I added a fuel return line from the fuel pressure regulator to the tank and haven't had any vapor lock issues since then. I think that providing a fuel return system that allows the fuel to bypass a "deadhead" condition where a heat sink such as a fuel pressure regulator or an engine mounted fuel pump could cause vaporization will deal with the VL2 gremlin.