Did you buy the AFB new? If not get a tuning kit and replace the jets and metering rods with the stock setup. I had a similar setup on one of my 360's. The metering rods have a large effect on fuel economy, also there are springs for the rods that should be checked. For stock settings try the Edelbrock or Carter website.
Beyond that check that the vacuum chamber on the distributor is good. Hook a hose to it, it should hold suction AND look at the breaker plate while you apply suction. It should move. Next make sure that you have the hose going to the distributor set to ported vacuum NOT manifold vacuum.
1977 CJ 7 360 T-18 IHC D300 FARM TRUCK NY
1985 CJ 7 AMC 401, CLARK 285SV 5 SPEED, DANA 60, DANA 44, RUBICON 4.5 LIFT. 37 KRAWLERS
1987 J-20 401 90% COMPLETED.
1985 J-20 360 6 inch lift, 37's plow truck
1986 J-20 360 stock well rusted plow truck
1970 AMX CURRENT PROJECT