These cars are VERY particular when it comes to plugs & wires. You can run a search in the troubleshooting & duratec maintenance sections for words like "bucking" & you'll come up with all sorts of horror stories.
The Zetec is less prone, but kennards situation stood out because it was sooooo extreme. Actually missing so bad he was shattering plug insulators. That is one mean misfire.
A good set of Autolite plugs & Autolite or new stock wires should do the trick just fine.
