well, after i got my turbo, i found out that there was a BOV in the box and its the exact same one in the above pic

now i need to know, since this kit did not come with a oil inlet flange, which do i need? the only thing i am lost on is that -3an -4an thingie. I did see on an auction that -4an is bigger and could possibly cause turbo damage since its "high flow" but the inlet hole on the turbo is the same size as the bolt holes (like ¼ inch)