2001 5.2l 5speed 4x4 running in 2wd 99% of the time

i am getting horrendous gas mileage, 10mpg, this is unacceptable. granted i do have a heavy foot but i should at least get 13 or so right?
what are all the things i should replace/service?
i put in a k&kn fipk over the summer so the filter is all set, running synthetic oil so thats taken care of.
i've been reading about autolite 3923 which spark plug wires to go with them? (mopar, accel, msd, etc)
i'd like to get the msd ignition system (distributor and amp) but that costs a ton and wont be til later
cap and rotor? which one/where?
differential fluid change - should i get it done at the dealership?
anything else i missed?