Sounds more like trash in the the bottom of the fuel tank, intermittently plugging the flow.
THIS is very likely the number one "cause" of so-called "vapor lock" for most folks who believe that they have vapor lock.
An easy way to rule this out is to provide a temporary fuel supply to the fuel pump. A plastic fuel tank for a small outboard engine works very well for this.
I use one anytime I break in a new engine if I do not have a brand new tank in the vehicle.
The hose on these boat tanks is the right size for the fuel line heading to the fuel pump, and the squeeze bulb works nice to prime the pump.
Carl
