94 Lumina 3.4L: MAP sensor or MAF sensor system?

I am trying to understand how my ECM/PCM controls the leanness of the mixture.

I think there are two different systems on Luminas, an older one (MAF?) that guesses mix based on manifold pressure and engine RPM, and a newer one that is based on a frequency-signal from a MAP sensor.

But it seems my computer may have both systems(?) working.

I think my car only has one O2 sensor between the exhaust manifold and the catalytic converter.

Does anyone have have experience with these systems?

Update: still trying to nail this down -

The Haynes Manual says:



Mass Airflow (MAF) Sensor

...on 1994 and later 3800 engines the MAF sensor is located on the throttle body. ...

Note: Not all engines are equipped with a MAF sensor, engines not equipped with a MAF sensor will be equipped with a MAP sensor.

...
Manifold Absolute Pressure (MAP) Sensor

...is typically mounted to the upper intake manifold or to the firewall.
...
To replace the sensor on 3.4L models, unplug the electrical connector and remove the sensor retaining bracket and bolt. Then pull straight up to remove it.


This seems to imply that (all?) 3.4L engines have at least a MAP sensor. Do they also have a MAF sensor?

In particular, does my 1994 3.4L have both?

Later the manual says:

... OBD-I engine control systems (ECM) have a single heated oxygen sensor located in the exhaust manifold.

I am wondering if this means that the O2 sensor has an actual heater in it, or does it simply refer to its location? I thought only OBD-II systems would have an actual "heater" style O2 sensor, since OBD-I would be the first time an oxygen sensor was even used...(is that right?).