There's a few rules:
* T off the Intake
* don't touch the vac line to the fuel pump
* distribution blocks are your friend
* T as close to the gauge as possible (limit the length of the vac line)
Unless you are planning to invest in a new intake mani w/ more hose nipples, I would suggest getting a distribution block. My vac lines were t'd to hell before I got my cyclone intake. Speed density, boost, BoV... I wish I had picked up a distro block early on. So much easier.
Quoting Iggy:
I'm trying to install my mechanical boost gauge right now, but I'm not sure which vacuum line to T into. I can't find an actual answer.