23 bar is good compression, but the fact that one cylinder is four bar below the rest does point to something possibly going on. The cold knock and gray smoke indicate incomplete combustion. Does it smoke all the time, or just under certain conditions?

Things I would check:

1. Valve adjustment. This is an easy one and the only one of the things I'm going to suggest as first checks that could directly affect compression numbers.

2. Intake or exhaust restriction. This would explain it being slow and still smoking.

3. Turbo boost. Low boost could make low power. If the ALDA has been messed with, you could get normal fueling without normal boost, which would give you smoke.

Also, did the injectors get pop tested and balanced when the new nozzles went in? If one or more are popping off at too low of a pressure, that could give you the knocking and smoking without anything else being wrong. While you're at it, change the fuel filters if they haven't been done lately. Sometimes a fuel restriction can paradoxically cause some of the symptoms of overfueling.

My $ 0.02.

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83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
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