At one point in time, mine was an auto as well.
Never had a problem with it.
Let it downshift on the hills and take it out of overdrive if hauling anything heavy.
I would get 25mpg hwy in the winter through the Appalachian Mountians. Probably higher in the summer, but I don't remember what it was.
Some slight differences between yours and what mine was, you have the EFI motor, mine is Carb. The 4runner vs. xtracab longbed, weights will be similar, but I think you have (had) a taller stance, so more air to push.
Just remember, these aren't race cars. Don't expect it to out run, well, much <img src="/forums/images/graemlins/lol.gif" alt="" />
Enjoy it!