Loose Bolt on Intake

I am not sure what it is but I would like to find out as I think it maybe the source of an air leak. On the intake manifold between the third and fourth cylinder from the front of inches left of the carb there is a bolt. The bolt is loose I have removed it and it does not appear to be broke but it will not tighten down. It just kinda of sits there. I am pretty sure it is not an aftermarket "fix" because the wear on it is consistent with the rest of the intake. Any idea what it is?

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