The ISC is the 6 pin sensor on the bottom left.
If I were you, I would:
Make sure the throttle cable is adjusted correctly where it bolts to the intake manifold. If the cable is bolted too far to the right on the manifold, the tb has no chance to close all the way.
Connect the idle switch. Make sure it is not threaded in too far. Look at the pic above and you can see how it adjusts in and out. If it's too far in the tb has no chance to close all the way.
Turn the BISS screw in all the way, then out 2 full turns. This should get the ISC somewhere within it's range to do its thing.
Adjust the TPS correctly.
Here is how. It is extremely touchy when adjusting. You have to be patient with it. Just tightening it down after clocking it will get it out of spec again. I've never seen or heard of one going bad.
If nothing changed from doing the above, I would then:
Do a vacuum/boost leak test. If there is one I would guess it's between the throttle body and head.
Test the ISC like
this.
Open the ECU and visually look to see if there is anything weird going on the board. If the ISC is way out of wack for long enough, the ECU will pay the price.
Swap the coolant temp sensor.