Hopefully going out tonight and see what it reads.

I know MErc had an issue with fuel pumps not delivering enough volume (with a service letter that excludes my serial numbers). Hoping it will be 42! That looks like a neck breaker to get at.

When the service manual states the pressure to 43 psi it is in reference to the manifold air pressure (or vacum), that's why you see 43 with ignition on before starting.
As soon as the engine runs there should be a 43 psi difference over the injector, i.e. between fuel rail and intake vacum.
To ensure the pump delivers full pressure when running, disconnect the vacum hose to the fule pressure regulator and confirm the pressure is still 43 psi .

Ran it last evening, and it was 43 psi wide open and running hard.

I guess I can scratch fuel off the list.

Thanks for all the help.

Next up is swapping the mirage + 21 p for a rev four 19. Bring the rpm up from 4250 to 4500 or so.

Had motor that ran like hell to 4000 & then stay there. Turned out to be coil. Motor then ran up to 6k as it should.