Mine was the opposite. I got the car back with all new plugs, and when they delivered it to me, it was misfiring badly. THey had to go back and re-code the injectors, and give me the car the following day.
When I got it back, it was fine, but the stumble came back on over the next couple tanks of gas.
Seems like most people are getting this after a plug change. I just had all my plugs swapped again, and that didn't solve the issue, so it's not like they put bad plugs in.
I think it's injectors, as I still have 2 of the old ones that haven't been replaced per the BMWNA bulletin, but lots of people have had all the injectors replaced, have hte new HPFP, new coilpacks, and new plugs, and still have the issue.
Makes me yearn for hte days of the old diagnostic machines, where you connected wires to all the plugs, and various other parts of the car. Obviously systems are quite a bit more complicated now, but the fact that it's not throwing a code shouldn't be exhaustive in determining that nothing is wrong. However rudimentary, I feel like mechanics were better equipped to diagnose a problem with one of these. Perhaps I'm just getting old.