How can i fix my vauxhall vectra b?

My vauxhall vectra b 2.0 dti has severe power loss. When i stop at lights, engine managment light comes on but when i get to 2-3 thousand revs it goes out but still the car is not pulling properly. Ive had this problem before and turned out to be the crank shaft sensor however this time ive ruled that out... Ive changed the mass flow sensor to no avail... Diagnostics said EGR valve, changed that, no joy! So ive checked all air flow sensors and pipes including vacum pump
and all seem in perfect working order... Ive even serviced it. Any ideas or help would be great.