Intake kits from aFe give your vehicle the air it needs by replacing the restrictive factory intake system with a high flow conical air filter, and providing isolation from the hot engine air. There are two types of magnum FORCE intake kits available for 2001 to 2004 Duramax: Stage One, and Stage Two. Stage One kits replace the factory air box with a housing and conical filter assembly, and may include a heat shield. Stage Two kits replace the entire intake tract all the way back to the Turbo or intake manifold, providing the ultimate level of fresh, clean, cool air to boost your performance.