I read this in the Australian Ford Forum , thought it was interesting and worth sharing. Air Intakes CAI: Cold air intake, great for reducing intake temperatures, great for power. HAI: Hot air intake (ok i made the term up), but here is how it works: Hotter air going into your engine makes for more efficient motoring, by increasing flame propagation in the cylinders and taking heat away from your cylinder walls. The ecu in an engine has whats known as an IAT sensor, abbreviated from Intake Air Temperature, the varying air temperature has an effect on how much fuel is pumped in. The hotter the air, the less fuel is squirted in with each injector cycle The colder the air, the more fuel is squirted in.. See where this is going? So by having hotter air flowing into your engine, you will lose a little power but gain on your economy and your throttle response somewhat. To do this effectively you can cut holes in the side of your air box before the filter, redirect your intake to suck air from around your exhaust extractors, or an area in your engine bay where there is a lot of hot air. From My link Thoughts ??