T it in to the hose that runs to your dump valve. If you have removed your dv then you should have a spare 'nipple' on the inlet for it to run from anyway...

I have T'd off the dv hose but dont have any pics i'm afraid. Mine shows -10 hg at idle (but dv diaphragm is split and causing an air leak, I think it should be nearer -18hg) and obviously it shows + psi when on boost)

HTH