ok guys,
I bought an 87 f150 with the 4.9 in it about a month and a half ago. It has 70,500 original miles, and I did my gas mileage, im only gettin around 10 mpg. I changed the fuel/air filter about 300 miles ago, and did an oil change and changed the oil filter as well. I know these engines dont get very well gas mileage, but come on, 10 mpg, i know i can get more then that. I also have a new exhaust on there. What can i do to help out my MPG here. Any suggestions are appreciated.
-Matt

 

I would look at these
Base timing (I set mine about 10-12)
Condition of your cats
Cap, rotor, and plug wires
Thats my .02

 

Also how fast do you drive on the freeway? What size tires are on your truck? These trucks get best economy at lower speeds 55-65mph. 33" tires on 3.55:1 gears make you lug bad on the freeway causing worse fuel economy too.

Check your EGR system as well as your TPS too.