yea, the instructions tell you to tap into the carbon canister, this is because the they're S14 based, on the S14 they have 3 pipes off it, one of which is a boost feed. DO NOT Tee into the s15 one, doing this well create un-restricted boost!
you have to get a nipple welded/tapped into the hot side of the intercooler pipework, install it like it was as stock!
isn't it a boost feed you want? not a vac?! taking one from the BOV will work, but, it's a long way...... best to keep boost pipes as short as poss' so as not to spike.