3.6L Idle - throttle microswitch?

[Tom '74 911]

Hello,
I've struggled with a surging idle and stalling issues ever since I installed an '89 3.6L engine into my '74 911 many years ago. Whenever I come off the throttle 100% and press in the clutch (like at a stop light or stop sign) the engine wants to stall. I've basically learned to deal with and drive around it, but it can be a pain at times...

Over the years, I've checked for vacuum leaks, checked the idle speed adjuster (#25 in the attached diagram) and anything else I can think of, but haven't been able to figure it out... I recently experimented by adjusting the micro switch that is activated when the throttle is 100% closed so that it doesn't activate and the stalling issues have improved greatly. There are some negatives to eliminating the switch, like a high idle.

My question is whether the function of this switch is controlled or can be dialed in via the "ECU chip"? I have an off the shelf 3.6L Steve Wong chip (911 Chips) that should help w/the lightweight flywheel that's necessary to mate a 3.6L to a 915 gearbox, but would be willing to get a custom one if it'd bring back the functionality of this micro switch...

I suppose I could ask Steve directly, but thought I'd start here first...

[walt]

Following. I have a similar problem with the same setup but not so severe. Idle drops quite low when I come off the throttle and if I have the A/C on I get an occasional stall. Did you clean the ICV and AFM? I would not mess with the idle switch.