Two additional things come to mind.
There is an inherent very mild whine from the timing chains on the Duratec. It is a bit subtle. Others have been concerned once they have heard the noise. If that is what you are hearing, it is nothing to be concerned about. It is sometimes called the "DOHC song".
Also the power steering pump sometimes makes a bit of a whine. The pump was redesigned in early 98 model year production. Nearly all of them prior to that made that noise. Mine did when new and the replacement pump had been redesigned. Even the new design can be noisy if worn. If the power steering is operating properly, some pump noise doesn't hurt anything.
