[V8] 5sp throttle body question

[Ron Wainwright]

I was staring at my car today and was just looking around the engine bay to make sure nothing lookes out of the ordinary cause of all the Black engine pieces I have it's hard to see any fluids that would be leaking.... but fluids shouldn't be leaking from basically a new motor :-)
 But i was looking around and noticed the throttle body and that vacume port that is cast into the manuals tb. Does anyone know what that vacume port is for?

 Ron the other V8 Guru