Ours is now 1100 kms old. When stone cold only, as soon as you start it up and drop it into gear, it splutters just a little and then that's the end of it. I figured when they do the 3000 km service they can reflash the
ECU with a program update which should hopefully fix the problem. In our case, if it doesn't go away it's such a minor thing that I wouldn't be overally concerned. Our last Focus did this as well.
Colville