built up 318 oddly low MPG's? hp rating?

yes i did.. do the ... mean that's bad? that's what all the tune up specs say to do. anyways I found this paragraph on this website. I said I was getting 16 in of HG in my manifold and indeed they say 16-18 is normal.

All engines require an acceptable air/fuel ratio to run properly, even at idle. Stock or mildly tweaked engines generally idle at 16-18 inches of intake manifold vacuum between 750 and 900 rpm. Carburetors equipped with adjustable mixture screws allow the tuner to change the amount of fuel delivered to the engine creating an ideal idle mixture.

http://www.mopar1.us/engine2.html