Unfortunately we are like the three blind men and the elephant without some data.
You probably need to see someone who can look at actual values and see whats happening. Without hooking my scanner to the car I never know on a 96/97 E320 whether I am dealing with HFM or ME fuel systems. I would worry about the throttle assy and all cables and/or linkage.
Bosch Master, ASE Master, L1
33 years MB technician