Getting a code 66, but mass air sensor seems to be within spec

[crazypete]

After a long hacking session isolating grounds, I am left with a code 66 (MAF cicuit below minimum voltage). Here is what I see

red wire: 12.4 volts key on
black wire: was actually 12 volts on power on, but I grounded it again, now clean zero

I see 12.4 volts between the two wires

backprobing the harness with the engine (barely) running, I see a potential difference of about 1 volt at idle, which jumps to about 2 volts when I tap the throttle linkage to about 4K rpms

For resistances, I see flat 0 ohms between black wire and neg battery post, about 0.75 ohms between the harness tan and blue wires and their connectors on the eec harness

Is this all ok? MAF's are expensive, so I dont wanna chuck mine unless it's really broken. But, as long as I need to chuck it, would I detriment anything by slapping a 73mm unit onto a mostly stock motor (exhaust and gears for now, only)?

Thanks all

Crazy Pete