Not sure if this one goes in the "Cold Start" thread, as I haven't really experienced that issue.

Long-story-short, my check engine light came on and the dealer figured out that it was from excessive carbon build-up on my intake valves.
They walnut-shell blasted out the build-up and returned the car to me.

Leading up to this, I noticed a reduction in performance which has since been remedied with the carbon removal.

Their suggestion was to start adding Techron to my fuel. Now, I'm all for this but I already use 93 octane Shell. I shouldn't really "need" to add this to my fuel.
Furthermore, should this even matter? In a direct-inject engine...the valves never really touch the fuel, so will this make any difference?

I've had some mechanic friends of mine tell me that this is more likely the PCV or ERG system. That there might be some sort of oil seepage into my fuel intake, and that's where the carbon comes from.
I know that carbon build-up can be common on direct-inject engines...but is there any real way to avoid this?
Will an "Italian Tuneup" help at all with this?

Nut shells and "magic engine soap".... this can't be the solution, can it?

I'm basically looking for the best way to avoid this in the future. I use good fuel, I don't mind adding some sort of extra cleaning additive(if it will actually help). I can open her up more frequently to try and cut down on the build up(again, if that will even help this issue).
I just don't want to have a standing appointment at my dealer to have the carbon blasted out of my engine....

Below is a readout of what the Mini diagnostic/repair report had to say, if it helps shed some light on the situation.
I'm going to ask them about the direct-inject engines with the advice of using Techron, it seems a bit fishy to me...but is there anything else I should specifically ask about? PCV? ERG? I know there is an oil-separator system built into the valve, maybe the diaphragm is leaking?

[size=1]Carbon build up on intake valves verified that check engine light is currently on. Ran fault memory and found 277b-cyl 4 misfire, 2777-cyl 3 misfire 2783-several cyl misfire. Found no other faults relating to the fuel or vanos system stored. Checked intake system for leaks or restrictions. Checked crankcase pressures and found to be good. Checked oil feed line for restrictions and found to be OK. Fuel pressure at time of faults for each cyl were OK and within spec. Followed misfire test plan and checked plugs, coils and connections(ok/good). Was asked to remove intake manifold and check for carbon buildup on intake valves. Found valves at cyl1-5, cyl2-4, cyl3-7, cyl4-6. Received authorization to perform carbon cleaning of intake valves.
Performed and cleaned. Reassembled vehicle and started. Ran a bit rough at first then idles smoothed out. Performed a fuel injector cleaning service. Vehicle is cold soaking over night for a start-up in the morning. Vehicle started up fine. Programmed vehicle(including CAS) and put a bottle of "crud be gone" into the fuel tank. Test drove vehicle after all repairs and vehicle is now running as it should.[/size]

 

Sorry for the duplicate, please delete.