I have wondered the same thing myself. I don't know if it is even necessary with these cars.... and if so what to use or how often. I hate to try something that is going to have adverse affects or end up wasted effort. Any input?.......
Not only not a problem, a necessity. Oxygenated fuels leave all sorts of gummy deposits, and can build up on injector pintles, intake valves, and piston crowns. Today's fuels have less detergents than they used to, as a cost cutting measure.
I advise running a high tech cleaner every oil change, or do as I do - Red Line SI-2 (in oless concentrated form) with every fill up for continuous cleaning.
The best products are:
Redline SI-1 and SI-2 (also has a top cylinder lube)
I am wary of BG 44K - it is an extremely strong cleaner, and Nutz and Boltz determined that it could cause delamination of coils in some FI designs. It seems to be a product for those that are already experiencing driveability problems - I say never let your car get in that situation.
Most of the other products are just cheap kerosenes. the better products have petro distillates, xylene, and other detergents. I have not noticed excessive discoloration on my plugs, but I do not read them so it is a possibility.
Once intake parts get dirty, it gets harder to clean them. Dirty intake valves can result in a lean A/F condition.