I guess I should add more here..

The engine ( and car) were rebuilt from the ground up. 67 coronet R/T vert. original engine and torque flite..

Engine was bored 40 over, forged pistons with a compression ratio of 9.2-9.3 to 1 after ccin the 915 heads.. Machine shop had the cam ( with about 1 inch of dust on the box) that was for a 375 horse 440.. Original carb 4327S, I think thats the number, rebuilt.. Stock original HP exhaust manifolds with a new accurate exhaust system including the "hi flow" hemi mufflers. I have just been cruising the car with only a couple of "breakin" heavy throttle passes. My stock points distributor was worn out so I installed, straight out of the box, a Pertronix billet plug and play distributor, and timed it to 7 bftdc pulling the vac advance line while timing.

Engine has a slight hesitation to it when I throttle it quickly and has backfired a few times when doing this.. I question my ability to rebuild the carb and I think the carb is pretty worn out.. I was going to install a new edelbrock but wanted to give the stock carb a try.. Was told it smelled very rich at warm start up by some friends...

Would a small vacuum leak contribute to poor mileage?? Thanks for all the help.. Oh and here is a pic of my 18 year project..