[comptiger5000]

Performance mods can help FE. Some, such as roller rockers, free up parasitic power loss, which helps both power and mpg. Others, such as exhaust, reduce pumping losses. If you get a set of headers well tuned for low end and midrange, you'll gain low end torque, and possibly FE. You can also tune the computer for good performance when you put your foot down, and be efficient at part throttle (more timing = more power and FE, but needs higher octane).