Re-read rapid340's post. He explains it. The purpose of the choke pull-off is so when you snap to WOT, the 2ndary air door opens slowly as the vacuum solenoid goes from the closed position to the open position. Yes it's just a couple seconds of difference but that's how it's designed.

Quote:

Is the air door held closed at normal operating temp. or when the engine is still cold.



Both. So long as there is vacuum, the 2ndary door is held closed.