Vacuum Lines

What exactly is the purpose of all the vacuum lines? I did the deckplate mod and want to free up the entire intake and am wanting to remove the resonator box and "clean up" under the hood. I've seen threads to just put a tee in another line to reconnect the one going to my resonator box. Does it matter what line I connect to? Are most of these for emissions purposes? What else can I remove and not throw a CEL?

 

I know vacuum lines have MANY purposes - of which I can't explain them all.

I'm pretty sure your brake booster won't work too well without vacuum.