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I always remove the pad in the 14 pin ICM connector. Pins are short and with the single bolt do not always make a good contact/

Hopefully we aren't chasing our tail. I think we centered on the ICM-ECM area because of the loss of E data that occurred? For the purpose of eliminating the one part that is common to every test so far, I think any borrowed 1990 Prom could be substituted. It seems that changing various parts does cause a change in operation so...? I think testing for continuity and possibly short circuits in the wiring from the ECM to the ICM may need to be done. It is pretty straightforward since the color codes at both ends are the same. Having a helper would be of great help here

The best situation would be to swap in a complete operational system from another 1990, including a different Prom. A big ask for sure, but if the tests don’t show anything, the individual parts swapping isn’t working. I don’t remember if I mentioned possible front of engine harness damage, inside the loom. I am not sure if the tests suggested above will reveal that or not? We need to definitely eliminate the ignition through ecm system as the problem. If it runs well enough to idle you can go through injector overrides to isolate a bad cylinder. How about six spark testers from Harbor Freight. Relatively cheap and gives simultaneous spark quality visual info.

It's very unlikely that you got two bad ICMs. Must be a problem with wiring or something. Install one of the new ones and run these tests to see if you can figure out what is going on. Reatta Owners Journal - ICM & Crank Position Sensor Troubleshooting