There is an excellent discussion
going on over at the BB about DI engines and carbon build-up.
After doing some poking around the net, I see that Ford is having a serious issue with it and BMW has been cleaning theirs for several years now (most of the German cars are having performance problems). BMW recommends a cleaning around every 35K miles. They perform a cleaning using walnut shell blasting.
One of the members has performed a walnut shell cleaning on his already and has started an experiment on rerouting PCV vapors. Thought I would post this for those that might be interested. It would be good to get either DDM or PAWs comments on the issue.
I am starting to believe I am suffering from this since I have been getting random misfire codes at start-up - cylinder 3 being consistent and where the PCV valves rests beside. I will have to take the intake manifold off to confirm. Car runs good after it warms up and I clear the code. Happens about once a week. My car has 33K on it as of this weekend.