well, i just finally changed my factory oem plugs at 100K miles with motorcraft platinums, just like came in it. i also put in new oem plug wires. the car runs a lot smoother. it doesn't shake as badly at idle as all zetecs do, and it accelerates and starts quicker. each plug is motorcraft platinum and was only $4.00 and change at my dealer. if you run aftermarket plugs, they won't last as long. put in what the factory did. the factory coil will last forever under normal conditions as well, making an accel mod pretty stupid. motorcraft wires ($34.95 at o'reilly auto parts) topped off my tune-up. a ford tech told me they're just as good as the motorsport wires (spark is spark). jmo.
