Car stalling AGAIN, Updates- none of them good. Options

[rjames]

Drove around for 30 minutes in 80+ degree weather. All arterial roads, so several stop lights, etc. No problems until I was almost home. Car stalled when I stopped at a light. RPMs just dropped to zero. Was able to start it again with a little difficulty and had to keep my foot on the gas to keep it from stalling out again. Power seemed ok though the rest of the way home (I think). It stalled once again at a stop light a couple of blocks from home and then again when I pulled in the driveway. I let it sit for 30 seconds, started it again and it idled just fine. Rock solid at 1000 RPMs. Pulled it into the garage where it sits now.

Prior to today the car has been running and idling perfectly since I went through the FI parts last year, which included installing a 123 distributor, new CHT sensor, a newly rebuilt mps (calibrated for correct afr on my engine), new vacuum hoses, NOS throttle body, rebuilt injectors, new fuel pump, valve adjustment and timing.

I haven’t checked the AFR since last year, not sure why it would change though.
It’s a ‘75 so the fuel pump is in the front, so I can rule out vapor lock I think.

Anyone have ideas as to why it would be stalling?

[rjames]

Do not assume anything is good until you 100% rule it out. Go to 914 rubber and buy all of the vacuum elbows, connectors, TB gasket, cold start injector gasket ect.. Auto Atlanta has a good vacuum line kit too, Put clamps or good zip ties on the plenum to intake runner hoses and also it is not unheard of to have a crack in the plenum itself.
Check the intake nuts for proper torque too.

For the electrical issue make sure as stated above, remove and clean the 3 prong ground for the FI and then go to every other ground one by one and do the sam

All vacuum hoses are new and have zip ties on them. Intake hoses are new. Gaskets for the intake runner, TB and cold start injector are new. I tore down all of the FI and intake stuff and cleaned it and checked the plenum for leaks

Used a smoke machine to hunt for any vacuum leaks. Used vacuum gauge at idle to verify vacuum was in speck (17inHG).

Bolt that grounds the 3prong connector on the FI harness was removed and cleaned up (it already looked fine but looks better now).

Vacuum doesn't seem to be the issue- at least not on the topside of the engine.

Haven't checked the ground point under the relay board. What wire is connected to it?