I had several of those same codes on my '93 2.8 liter M104. It required a new MAF and O2 sensor to fix things up. Based on your description it sounds like the engine is running on the default fuel map - basically not using either the MAF or O2 as inputs to control the fueling. My car was doing the same. And it ran surprisingly well, though the idle quality was lousy - rough and surging, though I don't recall stalls.

In my case replacing the MAF cured the pin 8/code 4 and the driveability improved greatly. The idle was still loping however. Replacing the O2 sensor smoothed out the idle. The car had 120K miles at the time, engine wiring harness had already been done. Throttle actuator is still original (and I'm scared to touch it...).

- JimY