My 104 surged too, I have a 96 so it was not the wiring harness but a vacuum leak from a bad Purge valve that was not closing. After that was replaced the car ran like new. If it isn't the cat it is likely something air related (MAF, vacuum leak, etc..) or your harness. Your harness connects all the electronic devices to the computer and the computer controls the idle, when there is a bad signal the computer will increase the idle to compensate for what it things is increased air flow. Good luck!
Brian

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Brian W. Heitman

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Your car has diagnostic code storage for the different modules/systems. So, you may want to go see what the Diagnostic Code System has stored for the HFM/SFI Engine Management module and the Accelerator Module.
This helps eliminate Guessing..
This can be done by looking in the Archieves for both the codes and the Tool needed to get them .
The tool is a simple home-made LED Retrieve device that cost about $5 to make.
These EFI units have quite a bit of storage capability and the pins I recommend you retrieve from will be both #8 [ HFM Module] and #14 [AE/CC module].
You have given the CE lamp activation codes , but they are not as refined as the actual systems ones for pin-pointing faults/conditions.........
..or, just have a Tech scan these other modules.

Hey guys/gals as always - You all have helped me save 100.00's of dollars. I spent $9.50 on 6 spark plugs and put them in myself (real easy on 1995 e320 ) Now runs great. The sparks plugs had white deposits and rust on them. The surging is sporadic / I think thats another issue. Anyway thanks again for everyone's help

J