Giving it some thought, all engines (not just the TFSI) will be making this gunk (especially during the winter) and it's not causing any harm to any of the others, bearing in mind the outlay of £300+ for this set up, you could get an oil change (if you really wanted) every winter for the rest of the cars life. . .
I personally need more convincing that the gunk is particularly harmful (it's like a bit of mayo round the oil cap after lots of short trips), the engine will burn it off after a long run.
My old focus ST got loads of gunk round the oil cap in the winter but would burn it away on a decent run. It's just oil emulsifying from bits of water vapour in it. When I asked Ford the said its normal on some turbo cars, and will have been considered during the design of the engine.
Gray
It's off the original topic this but You need to have a good knowledge of DFI'S to understand what I mean, forget the old oil filler cap thing!
(I really don't mean that condescendingly by the way I'm just trying to explain)
On the 04- VW gti's The fuel is not injected through the inlet valves like on your Old ST was
It's massively different in design
Although the brand new focus's are DfI's & they will get sh*tted up like our VW's I guarantee it!
I had an 07 40k mile 997 GT3 stripped last week and the inlet valves were as new ( engine tired though) I also stripped Doms Ed 30 at the same time, after a recent poor rebuild & clean he had carried out, the DFi golf's inlet valves were badly sh*tted up again after only a few thousand miles! The GT3's were as new but it had led a very hard track life!
Frequent Oil changes etc will not stop this nor catch cans they will help but never stop it
Turn the DFi into a normal efi and it will stop it!! but then the magic is lost !
It's the lesser of all evil, DFi = massive leap in the petrol engine power envelope + economy