1985 Buick Century Starting Trouble?

Sometimes when the car is cold, it has trouble starting. It floods out and miss-fires. Then if you hold the pedal to the floor and keep cranking and cranking it will fire then run normally. It has had tune-up(plugs, cap, rotor), o2 sensor, fuel pump, fuel filter, head gasket, rebuilt tbi unit. What else could be wrong? Weak coil? Ignition module? Any ideas appreciated. Thanks!