A spark plug that conceals the spark with electrodes, such as a Bosch +4, will not work as well as a plug that exposes it. The greater the surface area of the spark, the better the ignition. The theory is that this will give more power, especially in high-compression engines. I've seen a lot of test data, and there might be something to it - but until someone runs a test on a Contour with back-to-back dyno runs swapping new, properly gapped plugs, I won't go so far as to say there's any power to be gained in this engine from the fine-wire. I've seen compelling evidence in other cars running various plugs, so I will say that a good plug seems to often give a little power boost - but it may be due to a factor that's not important in our car.
