I need your help with my vacuum tap (and my manifold studs, too).

I'm going out on a limb here but it would make sense if the intake side of the threads were tapered to help ensure a good seal and since not all nipples are made the same I would think that it would be normal for some threads to be showing. If it were me I would put a little Teflon tape on it either way just to make sure everything seals up nice because vacuum leaks are a good way to create some gremlins that can take you forever to track down