That is indeed A boost/vacuum line.
BUT don't use that one, it's used for the fuel pressure regulator... .. the short of it.. you risk blowing up your engine if the fuel pressure regulator doesn't see the correct boost/vacuum.
the thing is... there are really only a few others:
-the brake servo booster.. avoid this as well!!!
-the PCV connection.. this is the one i'd recommend.
Get the biggest tee that will fit in that hose, then reduce from there to your vacuum line.
this is what you marked in red. in my car it stays collected (blocked) PCV problem or the manifold wants more air? if I remove it it doesn't emit smoke, if I put it on it does emit smoke