Dunno about that, but they had a serious problem with spark plugs
seizing to the head, and exhaust manifolds rusting out.
04+ 3v mods have a really long reach spark plug, the extended part was crimped onto the nut part. Carbon would form between the extended part and the head and stick them in there and they would twist off the nut. The updated plug is all one piece.
The exhaust studs get that weird steel vs aluminum corrosion and combined with the different expansion rates of cast iron and aluminum they break and cause exhaust leaks. Not really common for the manifold itself to break... they do but to a certain degree any cast iron manifold can.
The 97-03 5.4's catch a lot of flack about plugs blowing out, I have 94k on my '02 and knocking on wood I haven't had a problem. It stems from a lack of threads in the cylinder head, nothing to do with the plug. Later heads have more threads which is probably what spurred the plug with more threads.
Usually it is the phasers that go out of the 04+ 5.4's, a couple grand if you don't want to do it yourself and an all around big PITA and it is all fixed up.
Personally I would rather worry about the plugs blowing out (which IMO the internet has blown way out of proportion) than both the plugs breaking off at service AND the cam phasers screwing up. I have resigned myself from buying a new truck until the 5.0's prove themselves. In theory they have both improved (and much simplified) phasers and the one piece plug... but I want to see how they stand the test of time and for them to age into my price range.
I found my "Ford F-150 Pickup 1997-2005" book and looked up when the 5.4 became available, it says fall of '96.