i have a 2001 ml320 with around 235000 miles on it, great runner, and i was getting a lot of misfire codes, i would clear them and they would come back in awhile. i replaced all the plugs,wires,and coil packs last year. keep doing it, so i decided to put a set of injectors in it. it ran worse than the original ones.when i started it up i got a lot of smoke and it ran terrible. so i put the original ones back in and the same thing, it is still smoking. never smoke a day in its life until now. ant ideas. help.