Erratic idle and engine running rough

Alright folks, I need some real help with this one, it is a doozy.

I have an erratic idle with my near mint car that is listed above.

Sometimes: Start car up, goes to 2,000 RPMs then settles instantly to regular idle (700ish without A/C, 1000-1100 with AC on).

Sometimes: Start car up cold, goes to 2,000 RPMs and stays at 2,000, or waffles between 1,000 RPMs and 2,000 RPMs, sounds really rough, eventually code 35 (IAC Issues) pops. Engine is clearly missing during this 1,000 - 2,000 RPMs issue.

Sometimes: The issue will happen if the car is warm (200+) but not 220 degree, again, code 35, 1,000-2,000 RPMs.

Always: When engine is at 220 degrees, shut off, and then restarted the issue Always happens. Again, code 35, 1,000-2,000 RPMs.

Note: Data below is reflected in all circumstances (normal operation + during erratic idle) - I do not know if these are relevant, but they seemed interesting to my uneducated mind.

-Exhaust 02 Stays Rich for 30 seconds, then goes Lean/Rich back and forth constantly
-Battery starts out at 10.5 volts and drops as low as 8.5


Things I have already done:
Replaced IAC
Replaced Throttle Body Gasket
Replaced Battery
Replaced Throttle Position Sensor
Replaced O2S Sensor
Replaced Radiator and Heater Core (this solved a pre-existing "running hot" issue)
Replaced Thermostat
Replaced PCV Valve
Replaced TCC Solenoid
Replaced all Coolant Hoses
Replaced Water Crossover Coolant By-Pass Tube
Fuel System Cleaning with Intake Manifold Cleaning using Motor Vac Fuel Injection Cleaning System
Cleaned Throttle Body
Cleaned IAC
Cleaned pretty much every terminal I can find

Prior work on the car done recently (likely unrelated to the issue, but noting just for posterity):
Air Conditioning Compressor Replaced
Serpentine Belt and Tensioner Replace
Rear Brakes (Full) Replacement (Calipers, Rotors, etc)
ABS Front Right Wheel Sensor Replaced
Spark Plugs and Wires

My current thought is that it might be an issue with the ECM or the Fuel Injectors, but with the Fuel System having been cleaned so recently, I was leaning towards ruling out the Fuel System.

Note: I have an Acutron OBDI reader that can give me live diagnostic data, I can provide data on specific points if it will be helpful.

Would be grateful for any assistance you can offer, sadly there are limited mechanics in my area willing to tackle these problems.