Hey, nice effort Dave, and a very good writeup with pics. Basically a manually controlled aux air valve operated by a toggle switch under the dash, all ripe and ready for further refinements.

You're reminding me here of how much time I used to spend on my '74 140 fiddling around with its newer AAV design. It seemed every other oil change that I felt the need for an inspection, cleaning and possible readjustment to achieve a more well behaved idle. I recall I replaced it once with a new (not at all cheap then for a a young owner like me and my first new car). I was then comfortable incracking open the old one to see in detail how it worked with the internal compound bar and shutter, now playing with it to make a good spare. I had the spare adjusted high and would occasionally swap it in when the engine was going through one of its rough idle periods trying to challenge my limited auto skills and technical abilities then.

These P1800 ones were quite different in design and operation. I hadn't known about them until now, more likely I forgot what I did know. Retrofitting the later ones to your engine was not overly trivial as I soon realized when spotting that kit on Skandix.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now