Hi everyone -

Well, it seems to be an idle position sensor issue as Saumil suggested. I cleaned idle control valve and even bought a new one. Having some experience with K Jetro, only suspect for fluctuating idle has been idle control valve (or as Porsche calls it, auxiliary air valve). I did not realize KE Jetro has idle position sensor switch as well as throttle position switch.

When I cleaned idle position sensor switch's connectors (to wiring harness), problem went away immediately. Switches are still original to this car so both switches probably should be replaced. But for now, it runs perfectly.

Thank you everyone for your input.

I do have one more questions though. When I replaced idle control valve, I was also trying to replace hoses. One has a connection for start-up valve and start up valve is secured by 2 hex bots. I managed to strip one of them (after soaking in PB Blaster for 2-day). Anyhow, do you have a recommendation for extractor/method? As there are electricals around, heat is not an option.