Is it all AFM related?

[Gtr2.7L]

'94 Ford Ranger 4.0L V6, Auto

Check Engine light came on intermittently accompanied by a stumbling idle.

Ran the codes with a scan tool getting a 157 and 158 (AFM signal too high, AFM signal too low).

Check Engine light is now on all the time. Engine hunts at idle.
The transmission refuses to shift into overdrive unless the check engine light is off, and when it does, I can expect a violent downshift when the engine is under load and the check engine light comes back on.

So are all these related....and is it an ECU interpretation problem, or an AFM problem.

Used testing probes and a volt-meter and BELIEVE I found the AFM output signal too low at the source.....but I'm not willing to bet on it and don't want to chuck in the 175 dollar price of a new AFM. Even the used ones are 100!