Black smoke is from partially burned fuel. You get it when the amount of fuel in the cylinder is too much to fully combust with the available air.

Is this black smoke for a few seconds when first flooring it, or does it continue to smoke as long as you keep it floored? If the former, your ALDA could have been tuned to "smoky" by a previous owner. If the latter, you probably have something limiting your airflow. This is most commonly caused by a dirty air filter, but can also result from trouble with the turbo or wastegate. Also, and this doesn't happen much on Mercedes diesels, your intake manifold could be sufficiently crudded up from the EGR that it's significantly restricting airflow. You see that much more often on newer VW diesels.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.