If it stays running after you get started than I would install the fuel gauge and verify the check valve in the pump assembly is not bleeding off the pressure when you turn the key off.If it is than you need to replace the whole assembly.Or look for an injector that is sticking open and bleeding off the pressure.
I did that with a test light, the injectors are firing. I have no engine vacuum when I am cranking the engine. Plugged exhaust?? Is that common with these?
Take the cap off the distributor and crank and see if rotor is turning.