I've got a 2nd Gen 24 valve and looked at an '03 w/4. 10s in it. My current truck has 3. 54s. Anyone got 4. 10s that is willing to give me an honest answer on mileage? The on board computer on the truck said it averaged 18. 8 MPG... ..... a little tough for me to believe. It's a screamin' deal on the truck..... but since fuel is so freakin' high now, I am a little concerned about mileage.