BBK now offers SFI approved performance pulley kits with a SFI approved Steel crank damper. Built from high quality CNC machined aluminum & Steel each BBK kit is designed as a direct bolt on to replace the stock pulleys that rob your engine of horsepower. Each SFI pulley kit is designed specifically for each vehicle. This pulley kit is designed as a 3 piece kit. As with our traditional pulley systems horsepower gains are approximately 9-12 rear wheel horsepower which is a result of the reduced drag which also helps with overall fuel economy. As with all BBK parts these SFI approved pulley kits offer BBK's distinctive quality that guarantees many years of top performance. Note:All BBK performance under drive pulley kits use existing factory serpentine belts Application:2001-2004 Ford Mustang GT