Glad to see you used the search feature first. What you found is just what it is, it is either the recirc servo or the dual servo. I have done more of the dual servo than I have the recirc. The best way that I have found to diagnose it is to pull the vacuum lines, plug them, and drive it. I have one of the old worn out dual servos that I plugged the ports on that sits in the special tool cabinet just for this job. When you plug the servo lines that cause it to quit defaulting to defrost/floor then you have found your bad servo. My own daily driver is a '93/960 and has been playing this silly game for probably a year or more now and I just have not gotten around to it, obviously I do not live in Vegas. I have had customers request to just leave it plugged and run without the floor/defrost setting as it is not cheap to stick one of these servos in and it does not overly hurt my feelings 'cause they can be just a bit of a bitch to do.

If I had to guess I would say that it is the dual servo over by the
accelerator pedal. You know my brother lived in Vegas for a few years and he said the town was great and that there where only three things he did not like about it, June, July, and August. Get that a/c fixed.

Mark