I used these before, they made my car act funny. For normal driving, use the Motorcraft double platinum. For engines with some mods (turbo, nitrous, head package) use the AZFS.22.C. Those are what I use with nitrous.
Anything but +4's those things cause more problems than they're worth. Plugs are plugs. Stick with a no gimmick motorcraft part and you'll come out on top. The plats really just last longer. Oh, and the stock plug wires on the zetec are pretty well insulated...just to let you all know. I saw one get dyno'd and they asked what kind they were because they were having trouble getting through them.