Help identifying hose from intake to driver's side valve cover

Can someone explain the purpose of the hose from the rear of the driver's side valve cover to the intake? It looks like quite a bit of oil is making it through and into the intake. I think this is the source of all the mess in the throttle body, supercharger, and down into the intake manifold. It's also leaking a bit around where the hose hooks on. Sorry the actual hose was removed, pics are of where it attaches.

Where it goes into the valve cover:


Where it goes into the intake. Clearly making a bit of a mess:

 

Looks like the pcv.

 

I've asked about this before, under a similar suspicion, thinking I would just throw a catch can on there and send it. It was explained to me that the PCV air circulates, and this is actually air going into the valve train, the air exiting goes through the PCV valve... I wish I could find the thread on this, cause I think someone took the time to make a diagram.

 

yeah agreed
its a recirculation thing for emissions
mixing dirty/oily air in with the fresh intake air
hmmm
thinking a minimal amt of air bc hose is post MAF sensor????

 

A catch can would probably be really beneficial. This seems to be the source of all the mess in my intake. There's dirty, oily residue from that hose connection all the way through the throttle body, supercharger, and lower intake manifold and a little in the heads too. Everything upstream of that is spotless.

 

https://www.tacomaworld.com/threads/3-4l-egr-vent-line.735123/#post-26358522

I found it. It seems counter intuitive (cause you're seeing oil after that), but according to @Dirty Pool , air flow is going the other way in that line. I am unsure if a catch can would be the right thing for that line, and that's the reason most people only install them on the pcv line. YMMV with forced induction.

 

I'd love to see tutorials focused on an individual system in a vehicle. Like an air system tutorial going over the intake, exhaust, and all the air and vacuum hoses and their purpose, and what you might see on other engines. It's easier to reassemble things and identify problems when you know the purpose of what you're looking at instead of a mess of mystery hoses you know you better number to put them back in the right spot. It's the major thing that's missing with all the youtube tutorials.

 

As others have alluded to, this is the fresh air inlet for the PCV system. The intent is for fresh air to be pulled from the intake tube, into the drivers valve cover, then down into the crankcase so the PCV can ventilate correctly.

With the supercharger, the fresh air inlet tends to conduct oil residue into the intake tube and cause fouling in the throttle body. I added a catch can to the fresh air inlet, although it doesn’t catch nearly as much stuff as the catch can on the PCV line. You can get catch cans with dual inlets to just use one for the same result.

 

Thanks for the explanation! Sounds like a catch can is the solution.