1980 Toyota Pickup cutting off

When I cut off my truck, it lags to cut off. It keeps trying to run for a second and it will backfire. Sometimes soft and sometimes extremely loud. The carburetor air/fuel mixture is backed off two full turns, I've got new spark plugs, wires, etc. New exhaust manifold gaskets and flange, and the timing is right. I don't think it has a vacuum leak but I'm not positive. Is there anything else it could be? And the plugs are gapped right.