Convert a naturally aspirated engine to a turbocharged engine?

Hello everyone!
A long time ago, I upgraded my 2.4-liter diesel engine (Multivan Syncro, year 1993) with a turbo kit. At that time, I simply increased the fuel injection by adjusting the simple quantity screw on the top of the injection pump. I also installed a coolant level sensor later.
Currently, the air-fuel mixture is fine at partial load, but it's far too rich at low RPM, resulting in a black smoke cloud when starting. (Consequently, the exhaust pipe's bumper is always black.) And in the higher RPM range, the fuel mixture is likely too lean.

"Has anyone perhaps converted an injection pump from a naturally aspirated engine to use a turbocharger's boost control? I was thinking about Audi 100 pumps. There's apparently a 5-cylinder turbo engine from around 1989-1990. I've already spoken to a diesel specialist at Bosch, but he couldn't tell me anything about it." They simply don't care about it, and they don't give it any thought.

I would appreciate any information and tips.
Best regards,
Olaf from Nienburg.

Deleted as requested.

Hello everyone!
I've also managed to find out a bit of information. It seems there was a 2.0-liter turbocharged diesel engine with 87 horsepower, produced from 1982 to 1990, with the engine code "DE," and a 2.0-liter turbocharged diesel engine with an intercooler, produced from 1988 to 1990, with the engine code "NC." Perhaps someone has one of these pumps lying around and would like to sell it. I could start working on it. Otherwise, I'm confident I can handle quite a bit myself. Grin!
Best regards, Olaf.