Well, I was towing home from a long trip and I noticed more that usual noise coming from/through my air vents. When I was on the pedal it sounded like a air blower then it would go away when I let off. I know what the fan sound like when it gets warm and the winding of the turbo, it was not either one of these. Engine light came on, but only about 100 mile later. I have asked, someone said it might be a vacuum that came loose??? Should I go to the dealer? Is it my turbo going out? When I shut off the truck, it does make a longer "air relief" noise??? Any help would be great.