Gee whiz, I am late to the party on this thread.
I want to suggest you look at different fuel injectors. Not bigger ones, but some that have many more (smaller) holes per injector. This will better atomize the fuel going into the cylinders...
I don't know if my ATI under drive helped fuel mileage a bunch, but it did free up 8-10 parasitic hp. And the engine runs a bit smoother.
[edit] forgot you could get some devices to adjust the air/fuel mixture to something like 15.5:1. That should give you another 1-2mpg. Zetronix makes wideband devices for that.
http://www.zeitronix.com True, the return on investment (ROI) is rather lengthy, but there would be bragging rights. *Besides, ROI doesn't stop lots of people from blowing money on things that actually drain money faster from their pockets...