VDO vacuum Gauge install

[fiftytakedowns]

So in the light of trying to figure out the problems of what is going on, I picked up a VDO vacuum gauge, that being said, I am not quite sure which is the most logical place to T off a vacuum hose.

I am thinking from the Fuel pressure regulator, or POST ICV

Input appreciated!
anyone else have any insight on mounting a VDO vacuum gauge?

Thanks,