04-06 YAMAHA YZF-R1: Graves Airbox Velocity Stack Kit (Plastic) The Graves Motorsports Velocity Stack Kit is specially designed to suit the new fuel-injected Yamaha motor. These new intake stacks mount directly into the stock airbox (or Graves Ram Air Box) without modification and are designed to smooth out the power curve, increase horsepower throughout and improve fuel efficiency. Power gains of up to 6 HP in the mid-range and 2 HP at the top-end are not uncommon. Note: Contents vary by fitment. Note: The kit includes 4 injection-molded plastic intake stacks.