Aveo 2009 throttle body issue

Hi Everyone:
I cleaned my throttle body and used tech2 in idle reseting. I noticed that the hose # 4 in the attached photo evacuate air after shuting down the car. The air make the throttle opened little bit. The mechanics here told me that this is normal. Is it?
Thanks.Attachment 11378

I will change the question. What is the function of hose # 4? And what it's name? And who I know that it is work properly? Thanks.

are there any answers to my question?