I have my defi vaccum source taped on the line between the manifold and valve cover and it seems that my defi gauge is reading 3-4 psi higher then what the boost really is.

I'm running a aem ems and have a boost cutoff at 9.5 psi and my gauge reads like 11 or 12 psi all the time

should i tapp into a different vaccum source and if so where would be the best to tap for the defi gauge and for the bov?