Vacuum/boost signal

Hello, I have a small b&m blower manifold that has only a small 1/8npt port on 5&7 runner's, this i will run to a gauge, however i need to run a line to the carb that is boost referenced and also a line to the boost retard on the msd box, these have the larger hose nipple than the gauge, so i was thinking i may be able to take the vac/boost signal from the port that runs directly in the middle of the floor of the plenum (I think it's for an EGR) So my question is will i get the same vacuum inches from the port runner as i will from the plenum floor? It's one of thoses things I'm not sure on till i suck it and see.
Hope some of you could give me some insight on this, Thanks.

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