I have noticed since my truck was new, sometime when I start it up, there is a noise (like a high rev or whine noise) that last about a minute or so. it does not show the rpms to be high - just normal idle rpms and if I hit the gas pedal quick, the noise goes away. At first I thought it was the AC fan but I turned it off and rolled down the window and I could still hear it. It almost sounds like a fan clutch noise. Has anyone had this noise and what is it?