Porsche Repair: 911SC cold start problem, cis fuel injection, fuel injector cleaner

Question
MY problem is very similiar to Dave's question. My 82 911sc was running perfect til I put some regular BP gas in it. I emptied all the gas, put in 93 oct, added Lucas fuel injector cleaner a few times and it eventually smoothed out. However, I've only been using 93 octane since and it sat all last week and now ROUGH, ROUGH start, back popping, barely idling.  Is this a Filter problem, and injector problem, what? Any help appreciated very much.

Answer
The CIS fuel injection system is for the most part a mechanical system. I have seen this happen a couple of times where the engine goes int a lean running condition and makes for hard starting and poor running.
Possible causes
- Gummed up fuel distributor head.
- Failing 02 Sensor relay. This relay powers the lambda controls and frequency valve that is used to adjust the mixture in closed loop.
- Low cold fuel pressures. Check the WUR fuel pressures. The cold pressure directly effects the starting period.