I find K & N filters are a placebo effect or very little gains on dynos if its already a high power engine like the RS has. I had one for years in previous cars, and cleaning was a PITA, it's an artform not to overload the oil and make sure the thing is dry first, and even though I didn't have any issues I'm aware of, fouling the MAF sensors isn't worth it over just chucking and putting a new filter in. If someone was really anal, just put them in more often, they are cheap.

I think it all comes down to the sound really.