The new hot rod magazine shows a new set of heads for the 4.6l they flow so much better than even there ported PI heads. I think they said 453 hp from the same engine by switching to the new style heads and cam. I think trick flow made them.

Cant wait to see someone bolt these puppies to a 5.4l truck engine and see what kind of numbers it can pull bellow 5200 rpm.

I know the heads in the new mag are designed to address the severe flow issue with the stock 2v heads.