Your right foot must be huge! Seriously, 4mpg? wow... At one time I got 19mpg with a stock 302, 4bbl Holley and dual exhaust, average was about 17, with headers and AOD I got 24mpg. If I dropped from 70mph to 65mph, my milage dropped as well. She loves to run @ 2000rpms, any less and my milage suffers.