I read a recent article talking about various ways intake valves form deposits, specifically on GTDI engines, and they claimed the main reason is the intake valves are exposed to the combustion byproducts in the combustion chamber longer than necessary and not having fuel wash it off (like on a port injected engine). This is opposed to the "common" belief of PCV systems not catching the fumes, aggressive valve overlap, etc...
So regardless of the actual reason, what adjustments would I make to reduce the amount of time intake valves are exposed to the combustion byproducts? Would it be advanced ignition timing, with retarded inlet valve opening? What's the best approach with adjusting the VCT?