First off I don't thinnk I'd be running regular gas. Secondly 2 1/2 turns out soulnds like it might be to rich and where is your timing set? You may also have the wrong step up springs in the carb resulting in a rich burn( springs too long) and finally if the acc. pump linkage isn't in the center hole, try putting it there. I'm running 2 500 Edelbrocks on mine with a tunnelram with a Muncie M-22 with 4:10 gears and easy running I average 16-17 mpg. It can take time to nail them in so be patient and let us know how you make out. Good luck