Air Filters: More air = More gas = More horsepower
Using a LighTech, BMC or K&N air filter will increase the amount of airflow into your engine. Your engine will sense the increase in air and increase the amount of fuel to your engine. Voila! More horsepower!
Keep it clean! An added benefit is that aftermarket air filters can be cleaned and reused. However, if you want maximum power gains, you gotta keep it clean!