Yup, that's about right. Waste-fire EDIS'es (Electronic Distributorless Ignition System) like the one on the Duratec require double-platinum plugs on one of the banks (I think its the farther bank). Anything less than that (that includes single platinum) will prematurely wear. Since buying three single and three double platinum plugs is really kind of a hassle, your best bet is to just throw double platinum plugs in all of the cylinders.
This is one of those issues that I'd like to see sticky'd or FAQ'd because it comes up every month. If the search function was up and running, I'd post some links about waste-fire ignition systems, but maybe someone who can explain it better than me will show up (Demon, Big Jim?). I found some non-contour.org links about it in the meantime, though:
LinkLink (Ignitions section)Hey, I found some stuff in the archives!
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