so ive done some more trouble shooting on this truck, drove it to south florida and then back to mississippi this week. It went through more water than diesel fuel....i dont think it is the cap. it holds pressure...I have a notion that it is the egr cooler. When going up a hill, there is a wooshing sound under the hood like a cooling fan kicking on, but the fan runs off of the serpentine belt, so i don think that is what is making the sound. I thought the turbo waste gate was blowin open, but the boost pressure does not drop when it makes this sound. and the tempreture gauge goes way up. This only occoured during the day when it was 85 degrees outside. I read that the warranty covers emmissions crap like the egr, so we might take it to the dealer this week...