Hi, I am preparing may exhaust manifold for reuse. There is a tube fitting which seems to be pressed in on the top side of the manifold, above the twin exhaust ports in the center, and there is a hole on the bottom directly below this. Is this a passage for the air going to the choke? I can't get a rod through it right now, and I want to know for sure what is going on before I take a drill bit and clean it out.