AEM's 05-07 Subaru Legacy GT Cold Air Intake (CAI) relocates the air filter outside of the engine compartment to deliver the coolest air inlet temperatures possible. A intake heat shield gives you extra protection against engine heat. Cooler air carries more oxygen, which translates into a more intense explosion in the combustion chamber to create more horesepower and torque. But that's only part of the power equation. Tuning the inlet pipe in length and diameter to match the engine's resonance helps move more air to the cylinders (think of your engine as a big air pump), and no company on the market can tune an inlet as well AEM can. AEM also monitors fuel trim correction factors and all OBDII sensors during R&D to eliminate leaning the engine out and/or throwing a check engine light.