Hi i need some help i have a vectra 150 cdti i have loss of power below 2k rpm then turbo kickes in and off it goes but with loads of black smoke.I hva had

new egr +map sensor + inletmanifold that sorted it for a day or 2 then it went bk to how it was but no engine warning light are coming up i have checked all the boost pipes and so on could it b injectors.