CIS-E Motronic Fueling Issues

So, currently having issues with cold starting/idling for my MK1, it has a corrado engine fitted (2.0l 16v 9a) running CIS-E Motronic engine management.

I'm only able to get the car to start/idle if I manually raise the metering head flap on the airbox.

I connected a fuel pressure gauge to the metering head to check fuel pressure delivery and it's running at around 92/93 psi (I believe for the 16v 9a engine it needs to be between 89-95 psi so no issues there)



Then I checked spray pattern and quantity of fuel from the metering head to the injectors by manually lifting the metering head flap, again all look a good spray pattern and equal quantity (dont judge the beer bottles I didn't have enough jam jars!!) Also 3rd bottle from the left looks slightly less however only cos the injector hose wasn't tightened enough so I lost a little petrol whilst I sorted that





5th injector spray and delivery is also fine.

Timing is spot on.

In my mind I'm thinking the issue is related to the metering head flap, or whether any/all of the following:

1) Control pressure regulator (CPR) / warm up regulator (WUR) faulty

2) Airflow potentiometer faulty

3) Idle stabilisation valve (ISV) faulty

4) Wiring to any of the above from ECU

5) Metering head flap needs adjustment

If anyone has any ideas or experience dealing with Motronic or Jetronic fuelling issues any help would be greatly received!?