just bought a 98 12v 120k miles it is all stock. it has 3.55 gears and auto trans i did take the factory air box off and put on an aem brute force air filter on th factory tube and it has a stright exhaust what do i need to do to get better mpg getting 17 now.

 

You can bump the injection pump timing. That will pick you up some power and MPG. Don't go any farther than about 17 degrees on a stock set up though.

 

Look here for some ideas: Better MPG