Link to one article that mentions it:
http://ecomodder.com/forum/showthrea...amics-312.html
Sorry the thread is so long, but it's definitely one that I remember showing results. You'll have to dig through the thread. The modder ran a dryer vent hose from his intake to in between his exhaust and the engine block. Noticeable gains in fuel economy.
Cold air does make more power. It does this by allowing you to burn more fuel at a given throttle opening.
To get the same amount of power as you'd get with a "normal air" intake, you indeed close the throttle some. But you're burning about the same amount of fuel you burned making that level of power, and a more-closed throttle means that your engine has to work harder to draw the air through that opening.
Warm air makes you open the throttle more for a given amount of power. But you are still burning that same basic amount of fuel, more or less. But since your throttle is open wider, your engine doesn't have to work as hard to draw the air in. This reduces "pumping losses", making the car slightly more fuel efficient.
-soD