Took some time to understand the words you wrote, here's my interpretation.
"""
take take the pin 9 wire, and attach it to a body ground, just to see if the maf makes a signal with engine running, just a proof of concept
"""
Did this before in a couple of ways. Connected MAF pins B and C together, and then tied to ground lug on car body. Engine only runs with pin D disconnected from harness, but measuring pin D on sensor shows 0.88-0.9V, and varies with throttle opening.
"""
no to find the voltage.....
if you have voltage on the sensor ground internally in the ecm
you have
-open within the SHARED sensor grounds in the ecm
-poor ecm ground, not chassis ground,,,,,, pin 40,60 anywhere to the terminal point, under the washer bottle is the location i believe
"""
Looking at the A9L board directly, the MAF RTN, pin 9, is not shared with any of the other sensor grounds. I chased down the wires going to pins 40 and 60, and they are terminated with lugs that are solidly screwed to the body. Pin B on the MAF is attached to one of these.
"""
to test this
one lead at pin 40 then 60, the other lead battery negative, with ecm powered up
"""
Are you asking for a continuity test or a voltage measurement here? I did both; continuity shows less than 1 ohm, 0 volts drop from pins 30/60 to ground points.
"""
also take a sensor any one, like ect or act, tps, UNPLUG it and check for voltage drop on the SIG RTN
"""
These signal returns go to pin 46, and, again, are not shared with the MAF RTN.