NGK Iridium IX Spark Plugs (BKR7EIX x 6). BKR7EIX is one step "colder" than BKR6EIX and Gap is. 03" (0.8mm). Colder Plug for Models Listed. Colder Heat Range 7 Spark Plugs. Set of 6. In short, select one heat range colder for every 75-100 hp you add, or when you significantly raise compression.
