Question: do you know what the tubing is called that goes from the top of the throttle body to the back side of the manifold?
Answer: What model in your vehicle are you talking about?
2002 buick century 3.1L.
The black plastic tube?
If I remember correctly that tube goes to the top of the rear valve cover.
I think they just call that the valve cover breather tube.
I have looked numerous places and cannot find a replacement for it. the rubber bushing (or whatever you call it) is warn and does not have a good seal.
Yes, that is a very common problem with that tube. Your best bet is to just go to any GM dealership. They will know exactly what you're talking about. You may have to buy a kit which includes that tube and that seal.