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BW mentioned above what most say to do. Run a relay from the battery for the ignition power to remove any power loss/noise through the stock ignition wiring.
Bill USN-1 on binderplanet has tons of information on TBI setups if you havent seen that yet. They have troubleshooting tips and power checks.
I have a factory harness with my TBI. It has 2 power leads to the fuse panel from the alternator (always hot). I then have the purple start signal wire that goes to the starter/solenoid. There is a second small purple start signal wire that goes to the computer to tell it you are trying to start. The ignition switch that the coil and such are powered on are hot in start/run - pink power wires.
Have you checked that little spark control module that normally bolts to the firewall?
I am pretty sure my power to the distributor is good to go. Even wiggling wires/connectors while hot I have steady power.
My TBI harness is aftermarket, but it is identical to a stock GM TBI harness. Your wire colors sound the same as mine.
I changed the HEI module, since I had a new spare one. Still no start.
I also checked the resistance on the pick up coil, it was at 886, so between the recommended 500-1500 range. The pick up coil wires/connector are good, no change in resistance while moving them. No corrosion inside distributor, still looks new, only 6 months old.
I am a bit foggy, but IIRC, and I could be wrong, the ESCM (Electronic Spark Control Module) is only active while Starting the engine (under 400 RPM). Once the engine Starts, the PCM controls the spark timing. So, if it was bad, maybe it wouldn't Start, but that probably wouldn't explain while it dies while running, unless it is sending some corrupt signal to the ECM????????? I might pick up another ESCM and swap it on, wouldn't hurt to have a spare anyway. I couldn't find anything in the FSM on how to test it, might have to look some more? Could be the ECM went bad, too