By glancing through the code (see related link; 132 pages) PVC appears to be allowed in some circumstances and not allowed in others. You can consult the code online for free through the related link.
3 Inches.
In pre-PCV (Positive Crankcase Ventilation) vehicles, that was a term for the crankcase ventilation pipe.
It's the PCV pipe.
I think you are referring to a PCV pipe, generally you will find a connection between the engine crankcase and your air intake, which is why it is called a positive crankcase ventilation pipe or valve
Just below throttle body, it fits onto a breather pipe runs from the valve cover routing under the intake manifold. A small pipe connects the pcv to the intake manifold
near throter body with hose connected metail pipe
At the back of the engine compartment, on the driver's side, you will see an elbow pipe. It has a short connector hose that fits directly onto the PCV Valve nipple.
Remove the rubber piece of pipe on top of your cam cover. it is the one connected to a hole with a grommet. unplug the pcv valve from the pipe. make sure you clean the inner part of the grommet. buy the proper pcv valve and reinstall connect it back to the curve piece of rubber pipe .
Could be a vacuum leak. Check the hoses in there and the PCV pipe.
PVC is plastic pipe, It's called a PCV Valve in Automobiles. PCV stands for Positive Crankcase Ventilation. PCV valve. Engine removal is not required on any Automobile, I know of just to change the PCV valve. Some are hard to reach but that is it.
just right of the exhaust manifold. little black rubber pipe/elbow connects to it.
from the front of the engine you will find the PCV at the left rear end of the cylinder head cover(camshaft carrier) its a black plastic item with a pipe/hose connecting it to the air filter to turbo hose.