he mentions PSI so we must assume it has PSI writte on it.
Firstly, golden rule of not making yourself not look an arse, never assume Check!!!!
He probably didn't even check the vacuum side.
If you have never seen a boost guage iof the type talked about here you really need to get out more.
On the contrary, I think it is you who needs to get out more.
Are you even looking at the same as everyone else ?
Are you??? Pictures ???
I am not going to continue this waste of time with you, clearly you must be referring to another "LETTER"
If you want to get techy, they are incorect anyway even the MONOMETRES as they do not register the normal air pressure first!!,ie add 14 or so psi.
If you want to get Techy then at least learn how to spell first........it Manometer
Clearly shows your level of intelligence