Just that black vacuum box under the intake manifold. To check and see if its working or not just watch the diaphram while someone else turns the key on. If nothing happens than its not hooked up. If it closes then it should be opperating correctly. If you had a f22 vtec then yours should work. If you had the regular f22 than i dont know if that one had the duel manifold or not.

Mine on my h22a isnt hooked up and doesnt work. BUT my friend with a 97 accord h22a does work. I can wax him any day of the week. But he kept his F22 tranny and i chose to go with the h22 tranny. So i dont know if that has any thing to do with it or not. My point is i dont really notice that big of a power diffrence with it being open all the time. But then again it has never worked so i dont know if there even would be that big of a diffrence.