FP, KOEO was 42psi but slowly dropped to 40psi, specs are 40.5-47psi.
FP, KOER was 36psi, specs are 30-37psi.

Nothing wrong there that I can see, I didn't even try the vacuum pump as it appears to be fine. Squeezed the vacuum line during KOER and pressure increased as it should.

The diagram shows a Pump Prime Test Lead being one of two orange wires which doesn't make sense. There isn't two orange wire but only one but there is a red wire. All wires go into a harness with no test connector to put 12V directly to the pump. I'll have to check AllDataDIY to see it shows the location of that test connector

Here'* the current waveform for the pump, KOER.

I had a thought. What if the EGR valve had stuck open for a bit and is now working properly? I couldn't find a EGR valve although several auto parts dealers list one for it.

Did some searching and although I find this odd, somebody states that some GM 3300 engines use a ERG valve and some don't! Another person state none do.

Here'* two scope screens during a start/stall.

Red=EST from ECM
Blue=5V Bypass from ECM
Green=RefHi ICM output ECM
Yellow=1X Crank Position Output to ICM

The two needed outputs from the ECM have dropped and restarted during starting. Unless the ECM is losing power, it'* defective. Annoying since although ECM was replaced in '03/'04, it only has about 5K on it! Back then, the ECM was dropping the 5V Bypass only, IIRC.

Update:

For anyone interested. The problem turned out to be bad injectors. One was almost a dead short which causes the ECM to shutdown and/or sometimes damages the drivers. The car started with that one left disconnected but the scope still showed a partial short which was another one on the other bank the read under specs. With that one disconnected also, it ran a bit rougher but the injector signal looked correct.

This is supposed to be a common issue with the injectors used on this engine. I'm waiting on a set of injectors now.