Measurements will tell a big part of the story.

The ECM is triggered by Edelbrock's own semi-proprietary distributor. It is a 7 narrow -1 wide window arrangement for both crank and cam sync. I "thought" it was optical, (tooth passes through a slot to trigger) but either way, the wires for it are laying in the valley under the manifold with ALL the rest of the EFI wires, including injectors, and alternator field. What's the recommended shielding material? I'll also try to isolate as much of that sub-harness as possible.

Honestly, the only common element at this point is the digital-6+ box. I had this issue when it was carbureted too. I have a spare and also 2 regular 6AL boxes.