Yeah the baffling has been improved in various versions of VCs for these engines over the years. The go-to for a long time has been the Dorman ones. They don't work any materially different from older stock ones like yours and mine, except that the baffles are a bit more effective at separating the oil. Everything else about them is the same.

Not sure about "performance upgrade"... all I can see is a K&N cold air kit and those new VCs. Nothing that materially changes anything or "requires" a catch can or anything else.

Sure there's lots of ways to route a catch can. Just like there's lots of ways to do lots of things. Just because they exist doesn't mean they're all equally good, or good at all, or even functional. If you decide to add one, route it like I said, and strutaeng said, SEALED, between the PCV valve and the port on the intake; it's the commonsensical way to do it, it works, and is in accordance with the way that the dirty air (the air that needs "catch"ing) is flowing.

Route the PCV back like it belongs. Changing the VCs makes no difference to that. Hooking it up right will cure any "whistling", as well as crankcase pressure since ... that's what it's there for in the first place. Working correctly, there'll actually be a slight vacuum in the crankcase. As said, those VCs might need an "in-line" PCV valve, if one can't be plugged into the hole in the VC; in that case, you'll just route the hose that used to go straight to the VC where it plugged onto the PCV valve, to a PCV valve with 2 hose connections on it; and you'll route the 2nd hose connection to the nipple on the news VC. Which if your new VCs don't have a PCV valve at all, then you hooked it up you just put hard full manifold vacuum on the VC, and that's gonna create weirdness with the TB anyway, because the ECM will try to close the throttle to regulate the idle speed in spite of all that extra air coming in via the VCs. I have no clue whether those VCs have an actual valve / orifice in them, or whether it's just a hose nipple; that's what you need to be figuring out first, not whether to add catch cans or breathers. If it's a valve, just hook it back up like it was before, because it IS just like it was before. Or if it's just a hose nipple, add an inline valve. It's just not that hard.

 

Got it first I’ll need to figure out if the VC even has a valve. I’ll have to contact summit tomorrow to see if they can give me more info on them because the site just says OEM replacement and it says it’s fits all the LS from the 4.8 - 6.2. I did connect the new VCs exactly the way It was with the old VCs. As soon as I started up the truck with the new VCs it had a whistle coming from the K&N filter and had a strong vacuum because the filler cap was harder than usual to remove from the filler tube (I could hear it sucking air from there). So it might not have a valve at all and just be a hose nipple like you said because it just seems like it had a full vacuum, since it didn’t do that with the old VCs and still isn’t doing that after reinstalling them. That’s why I started doing some research but only found limited information on it. So the Dorman VCs would be the better choice? If so I’ll probably just end returning the new VCs and getting the Dorman

 

I don't think you need to do anything THAT drastic, necessarily; just, if all that is is a hose nipple and not a PCV valve, add a valve. You can go stand in front of the rack of them on cards at the corner parts store and probably find one that will work fine by just looking at them. $5 or some such and you're down the road and happy.

You can probably shoot some low-pressure air through the thing on the VC and figure out right away if it's a restriction like a valve or orifice would be.

 

I will try that thanks 👍