I have this same issue on my 1992 318ic. Started after I replaced the head. New hoses under the intake, new ICV, swapped the MAF with a used one, also swapped coils and wires, replaced plugs, new o-rings on the injectors, recent fuel filter, fuel pump is only about a year old, swapped cam sensor, replaced the coolant temp sensor. I am out of ideas and need the advise of those more smarter than me.