Our head rocks on the XP! We picked up 5 peak horsepower and 7-8 through the mid-range. This head kit provides increased cooling capacity keeps the motor running cooler, quicker throttle response. Low, and high elevation domes are available. Kit comes standard with 2 domes, billet head cover, and complete instructions. A very noticeable increase in acceleration and throttle response without sacrificing reliability with premium pump fuel. Easy bolt on power that works!!