Someone here was trying to reverse engineer an AFM maybe six months ago.
Please excuse, I don't recall the name (senior moment) but many of us sent
him our resistance data from old/working AFM's at the time. It might be
worth doing a search before embarking on one's own course.

AFM's are available rebuilt for something like $150 at places like Autobarn.
I put one in my 1.9 a year ago and it's working fine.

Given the loose resistance specs the Bentley calls out, I have the feeling
that it's not really that precise a component anyway. According to Bentley,
if the resistance "changes," it's good. I could be wrong, but that and the
fact that the 1.9 will run without any AFM at all tells me it ain't like a
carburetor in importance.