Let Me tell Y'all about My experience, with the idea that mayby someone can benefit.
The car--85 535i auto trans, 97k miles
Symptoms--drivability--When accelerating from rest, with a constant throttle position the engine would alternate between pulling hard and hitting a flat spot. It would do the same thing with full throttle. When it was pulling hard the mpg meter would show low mpg. Rich = power. When the flat spot would occur, the mpg meter would show high mpg. Lean= low power. In checking the O2 sensor a number of times with a volt meter and idling, it appeared to be ok. Readings between .1 and .9 and constantly fluctuating. Then Yesterday when checking it again--same kind of readings--then sometimes 0 volts. Put a new sensor in. The difference is like night and day. Now it responds like it should. Now when accelerating the mpg meter moves to one position and stays there until the speed builds, and then it gradually increases, like you would expect it to. I paid about $50 for the sensor and spliced it. My thinking was any 3-wire sensor would do. Hope this helps someone.