If you are running more modifications that require more boost, then it is a good idea to run a colder plug. The NGK Iridium IX Spark Plugs are designed to offer extreme ignitability, improved throttle response, and superior anti fouling.
The fine iridium tip is more durable, and longer lasting than your conventional spark plug. Iridium alloy has an extremely high melting point, which is needed for the high performance boxer engine. Other features for the NGK iridium plugs are Trivalent Metal Plating, superior anti-corrosion, and anti-seizing properties.
These are recommended for higher horsepower applications where a higher heat range number or colder plug will increase the spark plug’s ability to dissipate heat.