Purpose of the vacuum switch in GSLSE
 

There is a part i lack that i believe is called the vacuum switch for GSLSE. What is its purpose? If its for the ACV I dont need it.

i'm actually not sure what it does, but if its not there you will fail smog really badly

No smig for me. Im thinking it may be for ACV switching. Id rather not drill holes in my firewall if i can help it.