The hose connection circled in red in the picture, what is this connection for?

Because I'm running a 3 port boost solenoid, mine is plugged with a small plastic cover but I just noticed today the cover is broken (due to wear and tear from heat), I'm not sure how long I have been running with this hole being unplugged and leaked.

Would this hurt performance or affect the tune in any way? and for those running 3-port, what do you use to plug this hole with?

 

thats a vacuum source that goes to the top boost solenoid, the stock one.

 

Solenoid return it is, thanks!

Looks like this is not required with 3 port boost solenoid, what is the best way to plug this without having the cap to blow off again?

 

3 ports have 3 ports. One of which can be plugged into this. The other 2 are turbo outlet and WGA.