Here is what I suspect is your problem. You are running Fenton exhaust manifolds that are not heating the bottom of the intake manifold. You have not mentioned water heat for the intake, so can we assume you are not using it?
Without heat under the manifold, the excess fuel in the runners drops out of suspension and pools in the bottom of the intake once the engine is shut down. Without the heated floors, the fuel just sets and makes for a hard start up. High heat vaporizes the excess fuel. Mine did the same thing till I heated the manifold.
60 degrees out side and 150 degree engine temp is not hot enough to vapor lock a fuel system. If the weather was damp, your blimp of the throttle in the traffic jam could have been from icing, and again, heating the manifold will cure this.
