Not sure what it is called or what it does.
On the picture it's on the bottom left
round cylinder shape that's on it's side
and has a small piece of hard pipe that bends to the right. (down in the pic)
I started my engine up and couldn't hear it or feel a vacuum . Not sure what it is.

 

well you really dont need it conected, i have a single and that part isnt conected. i forgot what its for but its not hurting you performance wise.

brandon

 

That is your secondary throttle actuator. It controls the 2 throttle plates in the upper intake manifold.

The double throttle prevents you from using too much throttle before the car has completely warmed up and can help prevent surging as you open the throttle. But it can also cause boost problems if it fails to fully open once the car has warmed up and it also constricts the intake tract.

 

there is a procedure for removing those secondary butterflys, you can leave the hose off if you dont want to use the secondary b-flys, but unless youre actually gonna remove the b-flys you may as well keep the hose connected.