jesus this is quite a thread. In post # 56 Stretch shows the location of X11. This is where you need to go.

Put the IAC valve back on and get the engine to operating temp. At X11 check voltage readings at terminal # 3 with your ground probe in terminal # 2. Voltage should bounce back and forth +- 0.5 volt variance. Avg. voltage should be 6-8 volts.

If voltage is constant, that means you have a fault with one of the sensors. This test is easy and can confirm a fault or eliminate a lot of suspects.