[Mac-Porsche]

Okay, so apologies up front as I've asked a lot of questions about my CIS! (and I know this is a persistent subject on these threads) - I'll try to be brief!

My US 1981 911sc has rough cold start issues. If not driven for several hours, it cranks many times, then either immediately stalls after firing up, or putters into a VERY low idle (200-400rpm) and slowly works its way to 1400rpm (takes ~10-15 seconds), then goes into normal warm-up routine. Drives fine after that. Settles back to 950rpm idle when warm.

Warm starts are totally fine. Fires up immediately.

Pushing the throttle during cold start does help and doesn't cause it to backfire (as I've read a lot).

Seems like it's starved of either fuel or air (or both)...
Checked fuel pressures:
system - 4.3 bars (I know, its a little low...)
ccp - 1.4 bar
wcp - 3.3 bar
ccp -> wcp time ~2 minutes
checked AAR, it's open when cold, closed when warm
Advance set to 5° BTDC at warm idle (950rpm).
Have a afr meter on dash. Adjusted idle mixture to warm idle = ~13.7.
Low-throttle = ~14.3, WOT = ~12.5 - 13.0 (all values warm, O2 unplugged)

Haven't tried holding sensor plate open when starting. If I did this, and it helps, what exactly does that mean? I've read to try this in several posts, but not sure what that's diagnosing?
I installed 10:1, 3.1L P&C set last summer - has had rough cold start since. Does it maybe need a lower CCP on the WUR (due to higher compression)?