I knew I ran across this recently ... this is from an article by Alan Caldwell, Panorama, Feb 98.
And, for what it's not worth, I agree that a cold air intake is pointless on a 911. With 1500 liters (around 54 cu. ft) of air being moved by the cooling fan each second (I think that's the spec for the later fans), that probably replaces all the air above the engine every 0.15 seconds ... not likely to heat up much in that time.