To test for vacuum in the valley;
put a Vacuum gauge on the dipstick, flip the PCV out of the grommet and plug the hole, them plug the breather. Start the engine but do not rev it.
If the vacuum gauge reads a vacuum, then yes the intake is sucking air from the valley.
If you get pressure there, which would be correct, do not let it get over 3>4psi, as that could blow out a seal. Don't panic, at idle it will take a while.