89 244 Leans out when hot (LH 2.4)

It pains me to admit this but this thing is giving me fits and I'm fresh out of ideas.

Symptom: After coming up to temp and then stopping briefly, (think running into bank or pausing for construction, engine on or off) it begins to starve for fuel. Misfiring and exhaust backfires. Barely able to climb a hill.

Problems I found and addressed
Intake accordion had holes, Installed New OEM hose.
Exhaust leaks around O2 sensor fixed. Exhaust system smoke tested OK.

Things ruled out:
Fuel pressure and flow tested. OK.
Replaced fuel filter-old one back poured, kind of dirty.
Good set of injectors swapped in
Cleaned fuse panel
Swapped fuel pump relay
Smoke tested intake OK
Swapped known good computer
Swapped known good AMM
Swapped known good coolant temp sensor
Watched AMM signal @ computer plug with vantage scope looks OK
Watched O2 signal @ computer OK till it leans out.
Checked flex plate tone ring OK
Swapped new crank position sensor

Also car has no codes stored.

Anything I am overlooking?

How do you actually know it's leaning out?

reading 02 voltage and looking at the plugs

What about knock sensor?
CPS?

NVM. You did the CPS

Never crossed my mind, thought it just pulled timing when knock was present.

I thought so too but nothing else makes sense. What about compression test?

Is the door for the pre-heat hose in the air box stuck open?

standard thing, 1989 lh2.4 car if it has the original ECU, remove dispose of promptly, replace with later 2.4 ecu.