I agree with checking for codes, even if the check engine light is not on.

Another thought - maybe you have a bad ETA (electronic throttle actuator). This car is throttle-by-wire and your symptom may be related to a bad ETA. They are made with the same disintegrating insulation as the engine wiring harness, and in my opinion should be rebuilt as a preemptive measure, just like the engine wiring harness.

Are you sure your engine wiring harness has been replaced? In an earlier post you mention that it looks good. Can you double check?

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95 E320 Cabriolet, 169K