put it in 2WD.
weight reductions. anything you don't need remove!
also less unsprung weight. ie lighter tires and rims/driveshaft.
underdrive pullys.
CAI that actually relocates lower with a snorkel so it isn't sucking in hot air.
use premium!

or alternatively...

convert to hydrogen
convert to electric
install a hybrid system w/ regenerative breaking
buy a new vechicle



hope that helps