there is virtualy no difference in possible problems between the 5.4 and 6.8 on the same years..

its basicly the same engine with 2 extra cylinders on the end.

the only real issues with these engines is possible spark plug blow out or rotting exhaust studs.

other then that they are stout/ and solid.

the plugs are only an issue if you dont look after em, and esp. if you dont check the torgue values when installing. that step is crucial.