Take out the quick disconnect and the extra fuel line and see what happens. Mine was having vapor lock symptoms after I installed the quick disconnect. After sitting in the sun for an hour, it would shut down a mile after startup. After 3 times in one day, got home and took out the quick disconnect, put the original length hose back on directly to the petcock and no more problems.
I think the "quick disconnect" part is when you take it off quickly after finding out it causes problems. IMHO.
I like the convenience of the quick disconnect, but I'll be pulling mine off this weekend after a couple of instances of problems.

Short trips and cooler temps everything is good, but the combination of interstate speeds and hot days have given me fits with a 'vapor lock' type of condition. I've popped the fuel cap and all, but as soon as she's cool, or I fill her up with fresh (cool) gas all is well.