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Tjts1, I'm not sure what you mean when you say "factory-installed warm air intake." Either way, I dont think a CAI could help. A CAI should bring in more dense air, which means the engine needs a smaller volume of it to produce the same torque, which means a less open throttle plate, which means pumping/efficiency losses. WOT is really the only time the engine takes advantage of the CAI, and indeed it should be more efficient at WOT, but I dont think WOT is applicable to a fuel economy discussion. The only two ways a CAI could improve fuel economy (not efficiency) is if the CAI actually brought in warmer air, or if you scaled down the motor to constant performance.

Vince, ram air is arranging the intake system to take advantage of the velocity of the incoming air to artificially "boost" the engine. Unfortunately it's been proven many many times that the effects are negligible until at least 130-140 mph. Or what the article says, I didnt read it.

I made some pretty broad claims here, let me know if im wrong.