Whistling noise

[KILLERkpd]

Hi all,
I have been trolling this forum and others looking for an explanation to my problem but I have not found any so I am going to ask the members here for some help.

I have a '03 expy, 103xxx, I get a whistling noise that really seems to be coming form the back of the truck, definitely not the engine compartment. I have read about pulleys, bearings, and belts. I am sure it is not the belt, my old expy has this issue. It really sounds like it is from the back of the vehicle.

The whistling gets pretty loud while on the gas. It comes and goes at idle as well. Temps have been in the 40's and 50's. I still get the noise?? I have an aftermarket K+N and an after market exhaust. Not sure what type of exhaust it is as it along with the K+N were on the truck when I bought it.

It almost sounds like someone jammed a tail pipe whistle up there or something or I have a supercharger-in the back of my truck......

Just hoping one of you can point me in the right direction to get rid of it.

 

[edadmartin]

whistle--in the engine compartment what is it?

Well , now that there is a thread about whistling expys Ill jump in. Mine just started a mild whistle ,also seems to go along with acceleration, like going up a hill. When you back off it stops. Sometimes now at idle,but not all the time. could it be a split vacuum line? What do you guys think??