i just did a cooler install..
the nipple on the pipe is what runs off the boost solenoid or something ...
fact is i dont really know where it ends but i know that running your car without that vacuum hose being run back into the cooler piping your engine will run unlimited boost and basically..
BOOM
I simply went to ricol and got a nipple put into my cooler piping.. hooked it up and kicked her over..
cost me 20 bucks
ricol is in sydney / peakhurst dno where ur at