[Rupesy]

I have same the same car. I've had that happen when the cold start injector mounting block on the front of the manifold cracked. Changed the fuel mixture and I was getting the same symptoms. Founds the leak, replaced the block and it went away. There are many other places to have a leak on this engine. It may be that you are just having an air fuel mixture problem and nothing too complicated. I would try to find a source of leaks first before moving anything else.

If you don't already have this pdf, do a search on Google for:
bosch k jetronic fuel injection system

It is essentially the same system as on the 928. It will explain a lot of the different components on the engine and the theory of operation.

Worse case scenario will be to mess with the mixture screw. Just make sure you know where you started.