My 03 seems to be a little noisier than normal and slugish at the bottom end. Once in a while it will snap out of it and act like it used to. Also my mpg has declined, and Egts are up 100-150 degrees from what they used to be. If you stand by the tail pipe sometimes you can almost hear what sounds like a miss in the rythum of the engine. Truck has 22K mi and no mods. Dealer said there were no codes. Any help would be great.