High quality spark plugs are a sound investment for a well tuned engine. Recommended plugs are NGK brand PFR-6J-11. The gap should be set in accordance with boost pressures. The more boost delivered, the tighter the gap. Typical gap settings for high boost 15 PSI and above range from 0.032" - 0.035". Reducing the gap sacrifices spark heat and reduces power. Expanding the gap leaves reduces the ability of the spark plug to fire at high boost. The gap setting chosen is dependant upon available spark energy and the maximum boost level.
Contrary to some thinking, thin element platinum plugs do offer a horsepower increase over copper plugs above 6000 RPM. They also last significantly longer than copper plugs. Copper does conduct electricity better than platinum and therefore should provide higher spark energy at lower RPMs. This can easily be offset by using low resistance spark plug wires and higher energy ignition.
Spark Plug Wires
High quality low resistance spark plug wires can increase the efficiency of the ignition system and yield higher spark output. When selecting spark plug wires ensure proper fitment of the coil and plug boots and adequate thermal protection. Stock plug wires have a resistance of roughly 650 Ohms/foot, which is actually comparable to some popular aftermarket wires. Accel 8.8 wires have been measured at 150 Ohms/foot. Also be sure that the plugs provide adequate noise suppression. High EMF radiation can interfere with normal operation of the ECU and sensors.