How can i fix my renault laguna 1.9 dci fuel problem?

Did i get bad fuel ? Car when switch on will rev 900-1100 and at same time blowing black smoke out exhaust. Have added various solutions to fuel, all only temporary solutions. WHEN TRAVELLING, inlow gears and at low revs, can be chugging along. 4,5 and 6th gears all ok. Have added solution to clean injectors, fuel filter was clean, and not clogged when checked.