If the hoses going into the heater core are real hot, but the air comming out of the vents isn't very warm, i'd wonder if maybe the heater core dosen't have some kind of dust or crud preventing the air from getting sucked thru it.
You may also want to make sure the duct work going from the blower motor to the vents is solid.. if you have holes or cracks in that ductwork, the warm air passing thru would suck cold air into it, cooling the warm air and giving you luke warm output.
The other thing to check, with this being a newer truck, is the linkage for the hot/cool slider control.. you may have the lever set to 'hot' but it may not be moving stuff mechanically to the 'hot' position.
