2004 Volkswagen Van T5 BLACK SMOKING AT 3000RPM

Engine Performance problem
2004 Volkswagen Van 4 cyl Two Wheel Drive Manual

I have a vw transporter van 2004 2.5tdi tdi130, it was running fine then suddenly lost power when under load hill etc, I changed the fuel and air filters and put some fuel cleaner through it, but when its running in neutral (gear) it will rev up but starts to black smoke at approx, 3000rpm any ideas?