I used the spitfires for a few years. Not sure if I notice any difference. I just replaced them with standard Bosch Platinums, and used index washers so the electrode does not block the path of spark/explosion toward the combustion chamber. However, if you look in the latest version of Excellence, you will see a Bosch ad showing Platinums with two electrodes claiming that it is a better performer than the standard Platinum, and another one with four electrodes, claiming that it provides the greatest power.
Now, as an engineer by training, we all know electricity travels the path of least resistance, and four electrodes would block the spark/explosion even more. So what gives?
http://www.boschusa.com/AutoParts/SparkPlugs/PlatinumPlus4/