Idle/WOT switch question

[Vic Norman]

I have a 1991 Audi 100 with the 4 speed 097 automatic transmission. I've
been having erratic idle problems. Read Scott Mockry's article about the
idle/WOT switch being a likely cause and decided to check mine.
Unfortunately, the switch on my car is a little more complicated than
normal - instead of a single 3pin socket connection it also has a 6 inch
lead with a second 3pin socket on the end and from what I've read it also
has some sort of internal potentiometer. My obscenely expensive Bentley
manual does a lousy job of explaining all this - nothing to explain what the
potentiometer is supposed to do, nothing in the wiring diagrams to show the
second connector.
Can anyone explain how to test this thing and whether all its functions are
really necessary. It's a $250 item and it would be great to be able to
replace it with the simpler basic switch if possible.
Thanks.
Vic Norman.