what does this do?

[Mental Wealth Doctor]

there are two hose attachments on the front of the block just left and down a bit of the vacuum tree, after re assembling {after pcv unit replacing} the lower of the two attachments, was left without a hose, so was bunged up. just want to be sure its not important? whats it for? is it ok bunged?

[Rnash2002]

i think one goes to the recirc valve on the turbo,dnt know if the other goes anywhere.
Could be way wrong though,just going off where mine goes.