Need to know if the idle mixture screw is unrepairable...?

 Reading an excellent thread on thesamba about AFM adjustments,

http://www.thesamba.com/vw/forum/viewtopic.php?t=356377&start=40

I decided to venture into the " my engine seems to run fine, but let me just make a few minor adjustments" realm and risk it all...

'84 Digijet, 2.2 L GoWesty kit into a 1.9 case.

 My idle mixture screw seems to be stripped (doesn't tighten or loosen). From original position I turned righty 11 turns (to determine "tight point" and it was loose as a goose, still.  I turned lefty a bunch of times, no change in depth of screw, no change in VOM (have the VOM attached to the O2 sensor end of the O2 wire (and to ground)  +0.8 volts).

WAG: I wonder if the PO screwed down "below the threads", knocking off some "catch", thereby causing the screw to be turning freely below the female threads. Something like that? I have no idea why the screw appears to be without a female thread match.

Any way to get that screw working again?  Anything to take apart to get at it?  Anyone else experience this "loose as a goose" phenom?  I can always order a new AFM (our friendly Pennsylvania vendor has them in stock).  Or does anyone have a spare willing to let go of?

 Thanks,

Skip