Could be an idle mixture problem.

You might try adjusting the ECU idle mixture knob. Note where it currently is and then try 1 or 2 clicks (or more) either way and see if idle improves. If there is no affect at all, then the idle circuit is not activating and you need to adjust the Throttle position switch.

Have you checked the exhaust CO levels? There is no real way of setting up these D-jets without an exhaust analyzer or AFR gauge.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5