Billet Head Kit - Low Altitude - Matryx 9R - Polaris Increase cooling capacity for lower running temps which helps maintain peak power, The low altitude kit gains 4-5 horsepower mid-range and peak horsepower, For sea level to 6000 foot altitude., Tune is requried for the 9R., 91 pump gas is required., BPR9ES NGK spark plug is by Bikeman Performance.