How hot is your motor getting?

This sounds slightly different than vapor lock, but has similar symptoms. I am not super familiar with Cool Fuel II but believe there are still two pumps, an electric pump that feeds the main HP pump. On the older VST systems there was a traditional mechanical fuel pump that fed the VST and HP pump. I just had my mechanical pump die on my VST system and thought it was vapor lock except I hadn't been running the engine for more than 5-7 minutes at idle. Turns out the mechanical pump indeed died and a new one installed immediately cured the problem.

Sooo, if you have two pumps, the first feed pump may have died or is on its way out. And for what its worth, I run wideband full time and when the motor died the AFRs immediately told me it was fuel related and not electrical.