This is the Stillen Stage II supercharger kit in its entirety. Note that the kit includes an aluminum intercooler to help lower post-compression air temperatures. This stand-alone air-to-liquid intercooler system is comprised of two individual coolers: A coolant pump and a molded plastic coolant reservoir. This intercooler system, along with an additional 1 psi of boost pressure, is the primary difference between Stillen's Stage I and Stage II supercharger kits. We picked the higher-powered, more expensive kit because we know how important intake air temperatures are to high-performance engines, especially when towing. The Stage I kit costs about $1,000 less than the Stage II kit, but you also have to sacrifice 35 hp at the wheels. We like that the intercooled system is CARB-approved and is also available with a 3-year/36,000-mile engine warranty.