I am hearing a noise I cant figure were is it coming from it sounds like if it was the airdog pump but I have got down on the truck when ever its making it is not coming from there and I dont know if it could be the vp .It sound like a humming noise and its always starts rigth after I press the accelerator and let go of it that sound comes up I tought it was the airdog because it kinda sounds like the noise that the airdog makes whenever you turn your key, before you start the engine. Eventually that noise goes away. What could it be?

 

The VP does make a noise when i got a new one it took a while to get used to the new sound

 

any other advise?