I was originally looking for information about the possibility of polishing the intake chambers while the head was still on the car, but that morphed into trying to find any correlation between polishing intake chambers and subsequent carbon build up.
While there were a number of articles talking about porting (making the passages larger) and polishing (making them smoother) I could not find a single one about the effect on carbon build up. The closest I got to the two concepts together was a question posted on VWVortex that was never answered.
So, I am uneasy about polishing the ports while the head is still on the engine due to the possibility of leaving metal in the ports, but the question still remains:
Will polishing the ports cut down on the build up of carbon?
Thought I would throw that out to see if anyone has any experience. I will continue to change my search terms around to see if I can find any information on the topic.