That is quite a common leak. I hope it is, because that is the way my 83 is.
I don't think it does anything other than control the EGR so it should be fine.
I really doubt the MityVac is faulty. First put your finger over the end to seal the MityVac and pump it, does it hold? How about with the hose and fitting? More than likely it is from the rubber fitting on the end of the MityVac going to the other line (if going to a plastic line I use another piece of hose to couple the two), or possibly everything may leak.
