Forgot to add that I had an old MAF that had failed and was replaced. I
swapped it in and followed the recalibration procedure called out in the
service manual: Key on and don't start engine until after the whine stops in
the engine (~15 seconds). To my surprise, the old, 'failed' sensor that had
been sitting in my basement for about two years (with plastic caps on ends)
seemed to work. Oh, well. worst come to worst, I've got a spare.

Curious now if the output of the sensor is analog or digital. Could be that
if the output is digital, an electronic serial number is reported to the
ECU. Calibration may only done if a different ESN is present than the one
previously recorded.