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What engine do you have in your Fusion? A 4 cylinder or a V6?
Ok. The noise you may be hearing will be caused by the intake manifold. There is a runner control that is in the plastic intake manifold. The runner control is actually a rod that runs through the upper part of the intake manifold. It has 4 butterfly flaps, one for each cylinder. What is happening is that the runner control becomes loose int he intake manifold and it will rattle with engine pulses and it will sound just like a valve tick or engine rattle.
To repair the problem, you will have to replace the intake manifold. This noise will not cause any engine damage, just damage to your ears because your ears are now tuned into it. But to make the noise go away, you will have to replace the intake manifold.