I've found that the 5.4l engine is pretty noisy even when everything is working properly. That being said, the 2004 5.4l is probably the noisiest of all the model years. But at least it doesn't have the sticking fuel injectors of the 05-06's which can hang open hydro locking those engines. The cam phaser noise is also well documented especially in the 04's and can sound a little like a rod knock but higher up in the engine. Also be sure to use at least the motorcraft oil filters. After market filters have been know to make the 5.4l engine knock as well.