I have pulled the connectors, no oil.

I pulled the main line fromt he brake booster and plugged it. It shut off faster than usual, but still wound down a bit. I dont know that the booster is necessarily bad though, because I have had quick shut-offs like this even with the booster connected. I just cannot seem to isolate a leak, because everything is leaking at least a little bit!

What I have noticed however, is when I pull a vacuum on a particular line, it holds indefinitely, but when it stick it into one of those three way connectors (all of which I have replaced), it leaks. The connectors themselves hold when i use my fingers to plug it, but stick one of the plastic lines in there, and it leaks. Does this mean I have to replace all of the plastic now? Is there a way anyone knows to get them to seal better? Thanks for everyone's help and putting up with my questioning through this frustrating problem!