I went from a Holley 1945 and noodle exhaust at 18 mpg to a Feather Duster 2-1/4" Head pipe, Offy, Holley 390, recurved EI distributor and some very mild port work. Freeway settled in around 22 to mid 23.xx mpg.
This was with no change to the gear ratio, transmission, or rear axle.
I had bare...