Rough idle issue

I have a super 6 intake that I am getting ready to put it on to my son's truck, and the port that you show, I tapped out under the carb and put in a pipe plug , with red loctite for insurance.
My 85 came to me with no manifolds under the hood/ but a pre egr intake and exhaust manifold in the bed. Just a 1 BBL for now but good enough to verify that I have a running engine. I have a super 6 setup for it too.