There is a hose that comes up from the intake manifold side of my 1988 740 turbo wagon. It connects to a plastic fitting that splits into a large connector for a hose that in turn connects to the turbo hose and a small connector for a hose that plugs into a metal nipple on the intake manifold. I broke off the smaller fitting when trying to replace the smaller vacuum hose. How important is this thing? Can I just plug the intake manifold nipple or do I have to find a new connector? What does this contraption do? Should I plug the whole thing? Thanks for all the help.

That fitting thing goes to your oil separator- it allows the crankcase vapors to go back into the engine to be burned. It's not that important (you can drive fine without it) but you may need it to pass emissions tests. It's a really cheap fitting too, and easy to replace.