Be sure to check the gasket between the intake and the carb, it should have four cut outs on the inside, these let vacuum up into the carb for proper operation.
How much vacuum does it have? 18" to 20" or more?
Sound like its really lean, check the intake to cylinder head gasket for leaks, and any vacuum hoses for cracks.
Double check the timing, (8 to 12 degrees with out vacuum advance).
Joe
