Install a set of BBK performance underdrive pulleys and see an average of 8-15 additional horsepower over the stock pulleys. Under drive pulleys increase engine output by reducing the draw of the engines accessories by slowing them down and reducing the HP they use. Additional and significant performance improvements can be seen by reducing the weight of the pulley versus the original pulley which is why we recommend the BBK CNC Machined billet aluminum pulley kits for maximum horsepower gains. ALL BBK pulley kits are designed as direct bolt on replacements for the current factory pulleys and retain full cooling and charging characteristics. BBK under drive pulley kits are vehicle specific and each kit comes with complete installation instructions and allow the re-use of existing serpentine belts.