Cooled intake air does not equate more power. As with Turbo's and Superchargers the idea is that more air mean you can push more fuel into the engine. So if you increase the amount of air that an engine can recieve and the engine cannot change to match it then you will almost never get any more power. So with a K&N air filter, allows more air the engine can match that little amount and provide optimun fuel to compensate. With a Turbo and such you force more air into the engine. When you force a specific amount of air you compress the air which in turn causes the air to increase in temperature. In most cases a small boost will not increase the Air temperature to create problems such as detination. An intercooler will cool the compressed air so that the engine can create a optimal mixture of air/fuel. Temperature is very important and can effect ever aspect, too little or too much and you get the same result. Also desity of air makes for better combustion. I was told by an engine engineer for Ford that the under the bumper air intakes are a waste as they are getting cooler, but less dense air from under the bumper. The best spot for air intake is just above the bumper when the Air temperature is cool, but it is also dense. All this equates to a better and more efficient burn. In the overall the engine is expecting a specific amount of fuel and air. If you start changing them you change the optimal settings. Cooler air doesn't mean more power it just means you can get more air into the engine without causing problems. But the Fuel system has to be able to match with more fuel to make an efficient burn.
