Something else to mention is that air to air isn't nearly as effective as water to air, especially come race day when you can pour ice in your coolant tank!!! Cheap = make and air to air yourself, hack a hole in the hood, or run pipes to under the front bumper, yet stil not be as effective as the water to air. Which brings up another advantage of water to air in most cases... it minimizes the piping = less boost wasted running through extra lengths to get to the engine.
