Roger, there's a lot of information here and it's kind of all over the
place. Sounds like you've been messin' with it...

Here is a set of suggestions that might help. Easy and free, too.

1. With ohm meter on the idle position sensor contacts, turn the small set
screw on the throttle so the switch just BARELY makes contact. (This is
easier if you have an audible signal on the multimeter.) Then, when  you
find this place, turn the screw in one full turn. That's it--don't mess
around any more. Check it again after driving: it should be in pretty much
the same place. If not, the switch or mounting device is faulty. (Make sure
the mounting screws are tight! That did me in for a while there--similar
symptoms to yours.)

2. Disconnect the wires from the idle stabiliser and connect the plugs
together. Set idle as close as you can to 950 using the screw on the base of
the throttle body.

3. Set timing using strobe. Reset idle as nec. to get close to 950.

4. Reconnect idle stabiliser.

(It should run pretty good at this point.)

5. If not, try turning the screw that controls the mixture on the AFM (allen
head, on top of AFM) in and out to richen or lean out the mixture. In is
richer, IIRC. Make sure you note how many turns each way you move it so you
can get it back to the original position. If this doesn't help, you may have
to take  it to a shop and have them put a sniffer up the exhaust to reset
the mixture. I know my 1.9 runs lousy with the mixture too lean. NOTE: if
you disconnect your 02 sensor and it runs better, that may very well be a
sign of a too-lean mixture, as the sensor tends to lean it out when the
engine is warm (closed loop mode.) Try enriching it first and see if that helps.

I doubt if this is an ECU issue. They tend to fail all at once.

Good luck.

Geza