Or even a spray bottle of water. That should create a stumble in rpm's instead of an increase in rpm's when you found the leak?

Yes, I think it is vapor lock, and yes, I'm having identical problems with my 360 and AVS. The puller mechanical fuel pump is made to pump liquid, it cannot pump vapor. So yes, high temps anywhere along the fuel line can be heating the E10 gas to the boiling point, and then you're stuck until things cool down. I have tried insulating my fuel line under hood without significant improvement. A very good point was made about the metal fuel filter attracting heat. They used to make a plastic filter with the same dimensions. I may try and find one of those and paint it silver??? My best solution may be to swap my stock 22" 3 core radiator with a new 22 or 26" 4 row core when I can get some money together.