I believe that is a four corner idle base plate. The holes on the outside of the transfer slots are the idle ports. There are four. Sine most cars benefit from a spacer, I would rather go that approach, myself. I would make sure there are 2 holes. 1 for the PCV, 1 for your vacuum gauge. You won't get an accurate vacuum reading if you use the same port where you already have a vacuum leak coming in (PCV is only a regulated vacuum leak).