thanks for the detail! I was wondering which plugs to go with, so this helps.Excess plug gap adds load to the coil. Wider the gap, the higher volts before the spark. Makes the coil get hotter and increases the chance the spark jumps somewhere other than the plug. With double platinum chips the gap remains constant until the ultra thin chip wears out the gap then grows quickly as you have soft backing material. Good platinums should last 100K before the platinum wears out. The rear plugs go first on a coilpack system. That is the reverse polarity side. Only Ford knows why. COPS should last much longer since only half as many sparks per mile, and no reverse polarity. PIC of DOHC plugs over 100K and you can see the back bank plug is loosing it's center electrode as the plat chip is gone. Rear gap open about 0.012" and front gap still factory.