So the symptoms of dying at idle until warm pointed to the Engine Coolant Temp sensor. I ordered an URO replacement and installed it. No change, so I started checking spark, fuel, hoses, etc. I swapped the AMM with a known good one. I then checked the codes, which showed a problem with the ECT. It was new, so I assumed it was the wiring. Spent two days checking and rechecking. Then I checked the resistance on new URO ECT sensor itself. It showed infinite resistance. I checked the old one. It showed resistance within limits. I replaced the new with the old one. The car started and did not die at idle or when accelerating.

Conclusion, I think the original problem was the AMM. I put it in my 944 and it bogged down some, not as bad as in the 244, but the 944 definitely showed a difference. And, I wasted two days by assuming that a new URO ECT was working properly.