So I just noticed tonight as I had my radio off which I never do, but when I accelerate I hear a whining from my engine, almost like a supercharger whine, just not as loud as I can't hear it with the radio on but I can hear it over my exhaust system. It did it as it was warming up and after it was warm. Is this just a normal thing I never noticed before, or what? 2005 4.6L, 60,300 miles.