quirkdiggler

My guy went to pull my manifolds off today to put headers on and found an air passage/union with a flapper choke butterfly looking thing between exhaust manifold and intake manifold.. Considerable size too.. Since the headers won't have anything to do with intake there would just be a huge opening in the bottom side of the intake.. He doesn't know what the hell it's for or what to do, but he guessed and bolted a plate over the opening and will find out when it's all back together if it even runs.. If it doesn't he doesn't know what next.. Any ideas what this ex/intake manifold union is for? Warm air for cold idle?? THANKS!