I have a similar prob on my 86 300e.
It had sat for a year, broken and when i started it, it fired right up and ran like a tractor. I put in fuel injector cleaner, and started pulling plug wires. To see which ones made the car not run any rougher. Swapped some fuel injectors around and proved it was indeed running on 3. Cleaned them up.. must have been enough.. it keeps getting better and better now. One looked like it had been dunked in an ice cream sunday. Really is a snap to take them off.. But a visual inspection isnt the best way to see if its working.

Best part is, the fuel injectors must have been too dirty for the windows to roll up.. Cleaned the fuel injectors and now the rear pass window is working.

__________________
1986 300e (runs like a top.. interior needs parts)
2006 GTO
2003 Mini S