Weird noise?

[sankeneyii]

I was driving my truck today and noticed a weird noise comin from the exhaust pipe. It sounded like air was blowing really fast out of the pipe, it was doing it repeatedly whether i was at idle or driving down the road. It sounded like the turbo was spinning on its own or something and blowing air out of the pipe. It went a way when I would hit the pedal but would return. I am still fairly new to diesels but am just curious as to what the noise is and if i should be concerned.

[el conquistador]

If it was cold outside and the truck hadn't warmed up yet, it may have been your Exhaust Back Pressure Valve right behind the turbo.
look it up and read some threads. cold weather cuts it on.