right manifold 340/360

I don't know what happened on that last message I sent. Anyway any idea what the diamond shaped casting on the 9376 manifold is for? Mine is an actual hole that had a tube bolted to it. I never bothered to see where it went to, I think maybe an EGR valve?
It's an exhaust gas recirculation port. I used to manufacture a 3/16" plate to cover the hole.