Strange Idle issue - CIS Problem? (posted for someone else)

[Por_sha911]

***High Life (a newbie to Pelican) is having problems starting a thread so I volunteered to start one for him. Hopefully he can receive and send PMs but if you can help post it here. If you have questions post it here and ask High Life to PM the answer. Lets help the new kid out. -Joe

Hello - Brand new Porsche owner here.

Background:

I recently purchased a 1981 Porsche 911SC with 78,000 miles. It has decent documentation - 3rd owner - Ive driven the car roughly 300 miles

Motor was out for a rebuild at 70,000 miles in 2005 (12 years ago)
There were many things replaced (Long list) - but from the CIS main components the following were replaced:

O2 sensor
Fuel pump
Rebuilt Fuel Distributor head
Remanufacutred Warm up regulator (WUR Model 0438140090)


Situation:
I am having difficulty diagnosing a rough idle situation.

The car will cold start with foot pedal half way to floor holding for 30 seconds or so to smooth out idle (a little rough to start) - but then the car runs phenomenal. 900 revs at idle (dead straight) and can drive for hours. I have taken 4 long trips with one lasting 2 1/2 hours with no idling problems or performance issues..
See video here: https://youtu.be/9dQfq41RSLw

However - Once I shut the vehicle off and try to restart - the car runs horrible. It will start with no problems - but will not idle. It will oscillate ("hunt" or "lope") up and down around 500 to 700 rpms and performance will suffer - I have little backfires or sputtering that happens upon acceleration. Its still drivable - as I drove it 30 minutes to get home after a car show this way - however it doesn't correct itself - it ran rough and idled rough the entire way.

If I leave the car overnight - It will start and idle at the 900rpm range - running like the car I imagined.. BUT shut it down to fill up with gas - then it runs like crap..
See video here: https://youtu.be/s_ V2NE8giFg

Any suggestions to the components I should test or change? Im not sure where to start - and this issue severely diminishes the use of this car..

I have searched and read through many threads (so I am working on educating myself) - I ordered a CIS fuel pressure tester and I can use a multimeter. I also have the Bentley manual. The CIS system is all new to me - so I made need some step by step help in performing the tests..
__________________
1981 911SC

[High Life]

Thanks Bill for allowing me in!

It looks like I can post..

Here is the second video of the poor idle.

https://www.youtube.com/watch?v=s_V2NE8giFg

[High Life]

Thanks Por_sha911!