Jims CIS page is always a good reference.
911 CIS Primer - Index
I have the first generation CIS, so I cannot help with the later Lambda system, but I would make sure the air flow plate and fuel distributor piston are set correctly.
As you can see in the diagram, if the piston does not drop to the correct starting position, fuel can flow to the injectors prematurely. This can be caused by a sticking piston or improperly set air flow plate.
And of course, using the pressure gauges to get system and control pressures in spec must be done.