08 f150 x-cab fx4 5.4 26k. When pressing on the gas pedal just enough to get the truck moving, i feel a vibration that appears to be coming from the engine bay, maybe the firewall. Anyone ever experience anything like this? If so, what was it?

 

Ive got an 07 lariat 5.4 with 26k and mine does the same thing, I cant really feel it, but I can definitely hear it. Its pretty apparent when you first start it, when its cold. I tried looking for something vibrating but I couldn't find anything loose.