8.5 mpg help

[grey88gt]

This might be way off, but if the plugs look good and its ideling right and you got good manifold vacuum say 16-22+ at idle, id say the fuel is going some where else. Have you checked to see if the diaphram in the fuel pump is cracked. Over the years I have had three diffrent pumps, one on 460, a 400, and a 2.8 v6 crack, the engine still run great but have poor fuel mpg. All of them was squirting fuel out the weep hole on the side of the pump. Just a guess probally not your prob but something ive seen before. Good luck!!!!!!!