The ride is a shortbus-9000lbs. (I know-the size AND shape of a house

) 245k miles with new Beans tranny saver injectors. I've taken 2 trips in it-both in hilly terrain-99% hiway. On its own over a 700 mile trip it got apx. 11mpg. The next trip I was towing a 2000 lb trailer for 500 miles and the mileage was closer to 9mpg. Power was ok (well-i wouldnt complain if there was more while towing.)
What would you suggest to eek out a few more mpg? What might I expect to get?