I have the RM cold air intake. I drive my NSX only on occasion (not much now as I am saving/waiting for a new clutch/jap short grs/ 4.235r&p). I believe the recommended cleaning schedule is supposed to be every 15,000 miles. I find that hard to believe, but thats what it says on the box with the filter cleaner.
I personally clean the filter every time I get an oil change. Thats about every 2.5K miles. As far as dust goes, the amount of dust that accumiltes around the engine bay isn't any different from when I had the stock filter box. I have the dealer clean the engine bay (takes alot of time but they do a great job).
On a side note, aside from the cool sucking sound you get when you accelerate this is not a worthwhile upgrade. Admittedly, when it gets cooler here (a rarity in Miami) you can almost detect a slight increase in power. But the bottom line is that you are better off upgrading the exhaust portion of the NSX for any real performance gains. JMHO.
After I got My RM cold intake, I just didn't see any reason to take it out. Eventually my mech. will funnel the filter element right behind the side (driver) intake, with light piping to the engine. That way the filter element is not in the hot engine bay. Not sure if this is a worthwhile mod either.
