Ok, there should be a steel elbow coming from your intake, underneath/in front of the #1 and #2 injectors (if a single piece-88 and up intake) This is the line that you use for your PCV
valve, which goes to a 3 way T that will plug into both your valve cover and your airbox, if this is a stock intake setup (some will route the line that goes to the intake directly to the intake piping, if they put a cone filter or other CAI
-type setup on their car)
There SHOULD be a nipple that comes out the front of the intake, right near the FPR
(it will be slightly above and to the right, if viewing from front)
There will also be a nipple on the back of the intake, that runs to the brake booster. I have seen a few intakes with 2 nipples on the back, and no steel elbow under the injectors, they are the exception, not the rule.
That nipple on the front is the proper nipple to be running all your vacuum-ran devices on the car. I suppose you could reverse the roles, rotate the lower steel tube 180 degrees and then use the upper for a PCV
line, but who wants to see a big black rubber hose?
Most people will install the vac block directly to the intake that way, using a 1/2" pipe thread 90 degree elbow that turns into 3/8" compression thread, which can then be reduced, or if you can find them, 90 degree bends with smaller fittings, like 1/4 or even 1/8th, even thoug most all the barbs and fittings are 1/4 compression (at least the ones I have dealt with)