Dave don't forget the 12 valve Taurus and Mustang GT come with a plastic upper intake manifold. My opinion of plastic is its nothing but junk. Look at all the problems with the Mustang GT. An aluminum intake with a good phenolic spacer can reduce upper plenum temps by over 100* as recorded by an inferred thermometer. I'm not certain if you could do this with the duratec but its worth a try.
