Hmmm.. FlyingWen has the K&N FIPK, Calmini Headers and Exhaust, the PVC is about 10k old, and haven't touched the fuel filter yet...
Your real problem is that on the freeway your speed and mileage are not accurate due to the increased tire size. Also when the tire size is increased the gearing should also be changed (neither the Taco nor the X have been regeared) so this means that the trucks are not running at the optimum rpms for the speed traveled, and therefore decreases the fuel economy. We have discussed this before when I got new tires.
I think you just need to order us some matching front ARB lockers and some gears and throw them under the Tree for Christmas. Then around new years we'll have a gear party and install them