well....u lost me there ...
There is no vac line that goes to the OVP..The OVP is an electrical protection circuit and uses/monitors NO vac

Anyway............
the vac lines at the intake are
1 line from the vac monitor diagnostic sensor [on left fender well]
1 line from the Fuel reg , and one from the SOVs for the egr and Air pump.
The line from the fuel reg goes to the same check valve as the sovs do , but it goes to the bottom [ engine side ] of the check valve so that it reads engine vac under all running conditions/loads.
But the sov line goes to the top of the same check valve . This is so the sovs can not interfer with the fuel pressure reg readings
and the vac is checked via the valve.

Need more info