Found this also about the 8.1 internal PCV valve:
Intake Manifold:
The intake manifold is a one-piece design. The intake
manifold is made of cast aluminum. The throttle body
is attached to the front of the intake manifold. A linear
exhaust gas recirculation (EGR) port is cast into the
manifold for exhaust gas recirculation mixture. The
EGR valve bolts onto the rear of the intake manifold.
The fuel rail assembly with eight separate fuel
injectors is retained to the intake manifold by four
studs. The fuel injectors are seated in their individual
manifold bores with O-ring seals to provide sealing. A
Manifold Absolute Pressure (MAP) sensor is mounted
on the top of the intake manifold and sealed by an
O-ring seal. The MAP sensor is held in place with a
retainer bolt. The evaporative emission canister
solenoid is located in the front of the intake manifold.
The positive crankcase ventilation (PCV) system is
internally cast into the intake manifold. There is not a
PCV valve. A splash shield is installed under the
intake manifold. The shield prevents hot oil from
contacting the bottom of the intake manifold, maintaining
air inlet charge density.
The L18 has an internal positive crankcase
ventilation (PCV) system, and does not
utilize a PCV valve.
