I have a 1995 E-320 and have been working with it's issues for quite some time now. I have replaced:

The fuel pumps
The AMM MAF Sensor
The O2 Sensor
All 6 Injectors
All 6 Spark Plugs and the 3 Coils.
The Fuel regulator on the Fuel Rail.

Before all this the Check Engine Light was on. Now it's off. The Code reader in the Battery Compartment blinks once. No Faults on the ECU.

The Idle Jumps in Neutral more than Drive, and less in Reverse. Whats left other than replacing the throttle actuaror?

Any suggestions would be great!
I think there must be a vacuum leak somewhere?

Have you read the codes on all the other sockets?

cleaning or replace the purge valve.

E320 16 PIN DTC Charts inc. pin 8, pin 14

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A Dalton