Does anybody know where I can find this? Attaches to the TB and I'm not quite sure where the lines lead to, so if anyone could tell me this also I'd appreciate it.

You were pretty damn close.
That is the Vacuum Manifold. I replaced mine. Couldnt find that boot as a seperate peice and had to buy all the connecting hoses for $120.

Here's the post on that. http://cadillacforums.com/forums/showthread.php?t=14070&highlight=Vacuum

Replacing this peice fixed my automatic park brake release.

Thanks! It was driving me nuts not knowing what it was exactly, having to call around and ask for an "uhhh....." was pretty degrading.