Hi All, I have a 1998 Expedition whith the 5.4L. Recently I started getting an engine knocking noise while fast accelerating or when it downshifts on the freeway to pass/overtake someone. At idle it doesn't make any noise and actually runs quite smooth and quiet, but if I sharply revv the engine it will slightly produce the knocking sound aroung 2000 rpms. Overall the engine seems to run just fine, good oil pressure, not overheating, and no check engine light. What is this silly knocking coming from?