Addition to this...
CAI (cold air INDUCTION, ricers say they have "intake" ) does draw air in from a different location than the stock system.
The stock airbox/filter is only sitting in the engine bay, with a rubber tube-thing that connects it to the hole in the fenderwell. Now, yes, both the stock and aftermarket draw air in from the fenderwell, but their at much different locations.
My MAC cai has a bend in it that sits the filter farther into the fenderwell than does stock. And a densecharger, I belive, puts the filter even farther down into the fender.
Now run your engine till its hot and open your hood. Feel all that hot air in there? The fender isnt air tight. Only the connection between the filter and fender is sorta-sealed. Theres several openings to the fender literally inches away. Thus, there is hot air still in the fenderwell.
So in theory, a filter placed further into the fenderwell will draw *cooler* air than one sitting in the engine bay.
However, I believe the true gains from a CAI is between the tubing diameter, smoothess, and new filters.
-smoothness relates to how the stock airbow has that flex section in it. Cant be good for flow.
-diameter plays a part, sorta. Same theory goes into exhaust piping. Smaller pipes (not REAL small) up the air velocity. Thus the air travels faster. A huge pipe may not let the air speed up and just have the engine sucking in dorment air from inside the pipe. This isnt proven obviously, but its a thought thats out there.
-and obviously a new free-flowing filter helps too.