There's an update:

The valve I was referring to is an Impco A7-242.

I did end up removing the outer cover on it for a quick inspection and everything seemed normal inside, I managed to do so while it was still installed on the lift.

I did manage to get the machine running much longer with very poor throttle response, I had to again apply vacuum to the MAP referencing hose ( orange hose on the valve ) and once it is running I disconnected the MAP sensor. This prevented it from stalling.

I have pulled up some specifications of this valve and the output pressure is supposed to be between 11.6-12.3 PSI, so my next step is to tap a gauge at the injector rail and check my pressure, I have a suspicion that my result will be much greater than the specification.

Does anyone know if a rebuild kit for this valve would solve an excessive pressure condition?

I will let you know of my result, I'm hoping this is the issue, since if not I will then be stuck on any further troubleshooting steps.

Also, I learned that you can pull fault codes from the small dash display, turns out that the factory password of 55555 is not accepted, so It must of been changed, since this was a leased unit many many years ago.

Thanks for tuning in, I will keep you posted on my pressure reading.