Possible timing curve issue? Also from my service manual, for poor acceleration, manifold heat valve sticking, accelerator pump piston leather too hard, worn, or lose on stem; faulty accel pump discharge ball, faulty accel pump inlet check ball, incorrect fuel or float level, worn accel pump and throttle linkage, or incorrect pump setting.
Other possibilities, cracked body, faulty body gaskets, high float level, worn needle valve and seat, excessive fuel pump pressure, leaking float.