Possible issues:
- Fuel filter
- Clogged sock in tank due to crud/rust in tank
- Cracked fuel line to top of tank from main fuel line
- Cracked fuel line into fuel pump
Vapor lock does not strike me as so likley since this is running and not stopped, unless that would be a side effect of the fuel system losing some pressure. But it is possible.
Good diagnostic note above IMO from Trailbeast BTW.....
