1974 Dart

alriiiigghhttt. who is bored? I have a 74 dart custom 318 2brl it starts but will not hold an idle. let off the gas and she stalls. I have replaced the carb, fuel pump,distributor cap/rotor, plugs, wires ,coil, voltage regulator. one owner 57,000 always serviced miles. I have air fuel and spark. vacuum lines are well enough not new but not bad looking or dry rotted. possibly the BS emisions stuff or ?