Black smoke from a tuned VW PD diesel indicates incomplete combustion. Added fuel without enough usable air, poor injector condition or unsuitable boost control can contribute. Removing a particulate filter also changes how much soot reaches the tailpipe; it does not correct the combustion fault.
Review the calibration and hardware together. Check airflow, boost behaviour, injector operation and intake temperatures before increasing fuel demand. A larger turbo or intercooler only helps if it suits the engine and is correctly controlled.
Monitor exhaust temperature under the intended load, particularly where an older ECU lacks suitable factory feedback. Excessive heat can damage the head, turbo and other components, but smoke or a failed part does not identify the cause on its own.
PD variants differ in turbo, injectors and supporting hardware. Establish the engine code and fitted components before planning changes. Repair running faults first, then verify the calibration with logging and repeatable testing.