Air flow meter not Mass Air Flow meter. MAF is on electronic fuel injection LH, HFM or ME, not KE.
You have everything right so I presume you looked the duty-cycle code correctly. If it isn't a code it is the lambda control system maxed out trying to compensate. It should be lean, Try resting your finger on the airflow plate to richen it up slightly. Does it like it?
The O2 sensor can be damaged or put to sleep by continuous running out of range. You should see a drop if it is working when you do the finger trick. If you can't get it to move, unplug the O2 sensor (under passenger side carpet). This should get you back to 50% duty cycle.
I worked on one just this week and the sensor was dead. I had to adjust the mixture manually and run the motor a while before the sensor came back. Pretty hard to do without a gas analyzer. A new sensor might be in order if you can't get it to respond.
Bosch Master, ASE Master, L1
33 years MB technician