Where exactly do I plumb this in?
I have 2 vacuum lines on my throttle body, one on the brake master cylinder and the other goes somewhere else

If you do not have an open port between the head and the throttle body the best thing to do it tap one. Assuming your not using AN hoses go to a hardware store and buy a 1/8 npt to barb conenctor, a 1/8 npt, tap, and whatever drill bit it wants. Drill close to the throttle body if you can and shove a rag back there to catch filings. Grease on the bit when you drill helps also. Don't splice lines to get a reading. You want a dedicated one on the manifold after the TB

Volvospeed S60R C5500