Another update on this.

I ended up replacing the MAF, it helped a bit but the car would still hunt for the idle, die and occasionally go into limp mode.

It was too stressful for my mother to drive it, so I got her a new car and took the benz home with me. It was mostly driveable by paying close attention to the idle and sometimes riding the brake with the left foot while keeping a bit of gas on with the right.

The alternator and the belt tensioner both died on me, and after replacing the belt tensioner I've driven it a few times just by charging up the battery real good.

Now here's the punch line. Without the alternator working, the motor runs just sweet as can be. Idles perfect, starts perfect, etc. At least until the battery drains and then it start to run like crap.

Could my issues have been caused by a bad alternator? Is the computer really sensitive to variation in voltage?

I'll be replacing the alternator shortly so it will be interesting to see what happens then.