i ran my 93 F150 5.0 w/e4od 4x4 down state i ran the first 200 miles at 60-65 and then 100 miles 75-80 on the freeway. i noticed that at 80 it seems like your pushing it hard. i was fairly happy with the 16.5 mpg considering the the high speeds on the freeway. i suppose if i kept my foot out of it i might get 18.

 

wow, that milage is great! I have the same setup and get around 15mpg overall. If you want to boost it higher look into a k&n filter or maybe a glasspack muffler. With your stock dual cats, the glasspack will give you a managed low tone. Adding a glasspack made my mpg jump an extra 1-1.5