All this is true, except I thought someone told me one time that condensed air is cooler, that it was a basic physical property of almost all matter, that, when condensed, it becomes cooler. I could be wrong on that one, though.
However, I know the reverse is true (except for freezing water) the colder you make something, the more dense it is. For instance, inflate a balloon, measure the circumference. Then put it in the fridge for 10 minutes, then measure it again. There will be a considerable difference.
Anyway, what I really wanted to say is this...the reason RamAir works so well is 1. You are getting cooler air "forced" directly into the intake. Normally, not only is the inside the engine compartment hot, but it's stagnant. RamAir is coming in at (or about) the same speed as however fast you are going, improving air flow, 2. Often, in RamAir there will be some sort of funnel before the intake. This, basically, takes the amount of air in a large opening and crams it into a smaller opening, esentially condensing it, increasing air pressure, and making it possible to get more air into the chambers...and as we all know more air = more potectial HP.
Of course, it, obviously, won't a huge difference, prob 3HP (if you're lucky) or less on an N/A car, but it definately helps.