S13 SR20DET CAS issue

[Quiche2192]

I'm having trouble idling and accelerating. Idling is very inconsistent and the engine will eventually stop if I don't rev it up. Revving it up sounds really bad. Breaks up badly. Once up there, it'll run ok, but getting up there sounds bad.

Running stock ECU. I checked the diagnostic LED and got code 11, which is the CAS code. Checked CAS wiring. 12V feed is good. Ground is good. 180 Deg signal to ECU is good. 1 Deg signal to ECU is good.

Thought it was the CAS itself so I pulled the CAS and found that both the 180 Deg and the 1 Deg signals were sending square waves with voltages ranging from 0.3 to 5.2 volts, which seems good.

Timing was set correctly.

So I am at a loss as far as what might be going on. I think it's unlikely, but I suspect:
- Grounding issue
- Bad MAF and ECU is just getting confused and throwing the 11 code
- Bad O2 sensor and ECU is also getting confused

Appreciate any input