Cold Air Intake Systems let your engine breathe in large amounts of cooler air, resulting in increased power at the wheels. Cold air intakes enhance the combustion process of your engine, which uses both oxygen and fuel. Cold air intake systems pull in more cold air, more cold air means more oxygen resulting in more usable power and torque throughout the engine's RPM range. Most Cold Air Intake systems relocate the air filter outside of the engine compartment or away from the heat of the engine for a cooler intake charge. Cold air is denser and heavier than warm air, which means that there is more oxygen in a cold cubic foot of air delivering a higher volume of air into the engine. Replacing your vehicle's stock air box with a cold air induction system removes one of the biggest restrictions on your engine.
Joe added a CAI to his car so his engine will breathe and perform better.