Sounds like a vacume leak but maybe not...When in the cab and driving, the whistling starts when braking (and it sounds like brake squeal) but it continues when stopped. When accelerating it goes away. When looking under the hood, it starts when the motor is idling but goes away when you gas it a little and does not come back. Seems to have something to do with RPM. Sounds like it is somewhere between the valve cover and the fuel injection stuff but can't pin-point it. Pulling the PCV valve or opening the oil fill cap makes no difference except for the change in RPM with the PVC valve. It did not do this when the rig got started from a cold start but started after going down the road a few blocks. Do I have ghost in theis rig? Thanks again and again. gj