you sure youre not hearing the turbo winding down? His Fuel pump is under the drivers side door. If you stick your head near the inside of the frame rail, you will see it, and you can hear if its still running. If its not that, stick your head under the hood when he pulls up to park it, pop the hood and listen as he shuts it off and see if you can find out where the noise is comming from. If I am thinking right(uh oh!
) nothing shoudl run after the truck is turned off. At least on mine nothing runs afterwards. He didnt put an electric fan on there did he?