Hello,
I have a 1993 945T. 127K miles.
Got the following codes recently: 2-3-1, 2-2-1, 1-1-3.
I have replaced the O2 sensor, which did improve mileage to ~23mpg on the highway from ~21mpg, but didn't stop the codes from coming back. Sometimes I get the 1-1-3 code, sometimes not.
The car idles at ~1750 rpm, but drives decently well. I have looked around for intake leaks and can't find any obvious ones. In addition to visual inspection for intake leaks, I used a small butane torch (unlit) to try and find any intake leaks, but didn't find any spot that increased the rpm.
The engine does seem to ping when more than half throttle and sometimes has trouble getting above 4500rpm under full throttle.

When I unplug the AMM, the car idles at ~950rpm, but drives badly with no power (as one would expect, I gather).

I have tried cleaning the AMM connector and plug, which looked decently clean, but this did not help.

I am considering purchasing a used AMM from ebay to try out.

Suggestions?

Thanks,
Steve