Volkswagen Passat smoking and bad starting

tandem pump failed and pumped diesel into sump oil. first indication anything was wrong, was a smoke screen James bond would be proud of. changed pump and oil. smokes very bad on tick-over and setting off. starts with effort and missing while in low speeds while cold. at 50mph plus no smoke and no lack of power stop at the lights and the smoke comes back. no warning lights on. any help would be greatly appreciated Graham