S8 v10 misfire

[mitch79]

Hi everyone, I've been enjoying my lovely 2006 S8 for just over a year now with no problems but in December I started to get the eml light flashing up when the car was being driven (shall we say spirited ) nothing seemed to feel different but as it was due a service I obviously got them to look into the issue, they plugged it in and said it was coming up with random misfires but mainly on cylinder 4, so to try to eliminate the problem the coils were swapped over but still came back with the same fault, then I've had the spark plugs changed aswell. The problem still persisted and on a couple of occasions the car was actually running quite rough but if I turned it off and on it disappeared. Back to the garage where they have now done a de-carbon and also new coil packs aswell but still the light comes on and now stays on until I get it reset with vcds. Has anyone had any similar issues as I'm not sure how much more to spend on her or bite the bullet and get rid which I really don't want to do.
:Confused