I had this same issue but I have the 3.4. While tearing it apart to change the intake gaskets I noticed that my cam sensor wiring had melted together due to the power steering leak softening up the wire insulation. I also noticed a high amount of fuel line pressure when I let it out through the valve on the fuel rail. This leads me to think the injectors have been running wide open. I spliced in a new pigtail and my gas mileage is awesome once again. It's worth a shot to check your wiring to the cam sensor. It really seems to make a difference.
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