Well, I put my extra A/F feedback potentiometer on the bench and tested that little screw.
With the pot in hand, between pins 1 & 2, or between 2 & 3, there is no resistance. This is to be expected as pin 2 goes to the ECU through the 'wipers; built into the air housing.
Between pins 1 and 3, I got 1,789 ohms resistance. By turning the small screw in question, you can fine-tune the resistance of the feedback pot.

So if my brain is still sorting all of this out, I'm shooting to 0.7 VDC across pins 2 & 3 of the feedback pot, installed. This is ignition ON, engine OFF. Hopefully, I can pull the 0.8 VDC back to the spec 0.7 VDC. With that little screw, you can tune down to 1 ohm.
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