Slight voltage changes = unstable idle?? ECM EXPERTS!!!

I own a 1989 Cutlass Supreme(2.8L MPFI) that I cannot for the life of me seem to figure out.
It's doing a LOT of strange things, that to me, are indicating a
faulty ECM.
First off, I've noticed that once the engine is up to operating temperature(200 degrees F'), it starts to get "sluggish" and the idle starts to act-up. I recently noticed something even stranger in that for some reason, VERY small, and I mean like 0.2-0.5 volts, voltage drops are affecting the engine. For example, if I turn my four-way flashers ON, and the four-ways flash ON and OFF...I can literally sit there with the engine running, and watch, hear & feel the engine kind of "stumble" a little when the lights go ON, and quickly smoothen-out when they go OFF...so as the four-ways are flashing ON and OFF, each time they go ON, there's a little hesitation in idle...then they go OFF, and it's smooth...it will just keep doing this until I shut them off.
My two biggest helpers in figuring out what's wrong is my AutoMeter Vacuum Gauge and my AutoMeter A/F Gauge(O2 Sensor). Going back to the above, every time the four-ways flash ON, I can see the engine's vacuum drop almost 2" hg to about 15" hg. When they flash OFF, it goes back up to about 17" hg. So as the lights are flashing, I can sit and watch the engine vacuum continue to flucuate up and down like this until I turn them off. So I KNOW that something really is happening and that I'm not just "hearing" things.
Now I should let you know that's it's not just the four-ways...it's ANY electrical load...even just opening the door which results in the interior lights turning on causes the exact same thing...I can also watch the battery voltage while this is happening with my digital multi-meter and the voltage isn't even dropping half-a-volt during these times!!?? It's always steady around 14.4 volts and might drop to 14.1 when the four-ways flash...
I've already made sure that it's not the battery or alternator causing any of this. Both are not even 1 year old and working perfectly.
Now, moving on...
For the past few weeks I've been getting a frequent code 45, meaning a Rich exhaust. My O2 Sensor is almost 2 years old. I've also got a code 44, Lean exhaust, once or twice. BUT!, here's the strange thing: A code 45 is only supposed to set when the throttle is between 3 and 45 percent, but my engine is ONLY running Rich at idle, when I'm at 0% throttle. Again, thanks to my AutoMeter A/F Gauge, I can see that 75% of the time I come to a complete STOP, my O2 Sensor sticks RICH and doesn't move...until I start to drive again.
Today, I was idling in Park...watching my A/F Gauge...it was going back and forth nicely...and then SUDDENLY, the SES Light came on, and the O2 stuck rich again!? All this happened in a split second...which again doesn't make sense because code 45 shouldn't be set unless the O2 is sitting Rich for 50 seconds, not 1!!
And again, the SES Light for code 45 has ONLY ever come on while I'm idling...even though it's not supposed to unless I am between the 3 and 45 percent throttle angle!!?
Last but not least...a few times in the past couple of weeks the idle will all-of-a-sudden go crazy! Three times, the car wouldn't start unless I opened the throttle(closed IAC)...if I could get it to BARELY run, I would pull over, shut if off, re-start it, and then everything would be fine!!?? It's almost as if the ECM is losing control of the IAC or is losing it's IAC memory and can't remember what to do with it...
So, to sum everything up:
1) Engine is "stumbling" slightly when voltage dips a half volt or less
2) ECM is setting codes even though criteria for code is NOT being met
3) ECM is losing control of IAC or "forgetting" IAC positioning
I'm guessing it's time to get a NEW ECM??
The only thing that's stopping me from doing so is the O2 Sensor. I know that the O2 Sensor is independant, and not "controlled" by the ECM...so why will the O2 Sensor sometimes just suddenly STOP above 0.7 volts(RICH) and not move!!??
Help is greatly appreciated!!!:) Sorry for being so long...
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The first thing to do is check all the system grounds for corrosion. The O2 sensor sticks rich because there is too much fuel in it....

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