[Boog]

I did put on a new alternator and that raised the voltage to 13.7 to 13.9. The engine still ran the same.
The cable does have the 10k resistor and is necessary for data flow on this vehicle. If I switch it off there's no data.
Also, that resistor will cause idle speed increase and timing increase as stated by the supplier Red Devil. That explains the wild swing of rpm when moving from drive to park as it doesn't do that when the cable is not hooked up.
Today I swapped the prom with that used one I picked up and it made no difference.
The fan clutch is a Delco unit a few months old and the thermostat is a 195* also a few months old.
I paid attention to the engine temp and the point at which the fan clutch engaged and that is approximately 190*. I covered the grille in an attempt to raise the engine temp but it held steady at 190 all while idling in park for 20 minutes. There are times when the temp did reach 198 but not today.
I removed and opened the ECM to inspect it and it looked like new inside. I examined the board and found no burn spots or weak solder issues. The plug terminals are all clean. I'm a mechanical guy. If I can see what's broken, I can fix it. I am weak on electricals. I don't know how to effectively test an ECM.
I checked to see if the case needed to be grounded and there is no voltage escaping through the case. I did notice the ECM got awfully hot though, almost too hot to hold onto. That may be nothing.