Op has stated that his installed valley cover pan has the close the cross over option. It was suggested very early on in this thread that his intake may not have this port,,,,blocking with the valley pan will give indentical results,,,,a cold or very slow to warm up intake.

Again I repeat, this is not recommended for a normal street driven engine. The lack of early and adequate heat to his intake manifold as oft repeated in this thread is a leading candidate for the erratic running issues that he had described.

The factory installed these ports for a good reason. Not anticipating they might be disabled by some tuner with a better idea.