I'm trying to read up on block and valve cover breathers. I know there are lots of custom options, but I'm going to start with mainly the OEM stuff.
Obviously the AEB 058 valve cover does not have a vent, but the 06A do. I've heard of people tapping the AEB valve cover but it does not contain the sectioned/blocked off portion on the underside you see in the image below. Is that just a plate with holes, or is there something else under there that is important in ventilation like some sort of screen?
(06A left, 058 right)
The only difference I could find between the valve covers besides the breather is the angle of the oil cap, and the tab on the edge of the 058 style you see below:
Why did VW make the valve cover with the molding for a breather for the AEB, but only include it in the later styles? What on the AEB makes it different to not require a valve cover breather, and also, why do people add them afterwards? I assume when adding more boost you would want the valve cover breather?
Now to block breathers. This is where I get a little (more confused). I'm under the impression that the 06A style vents crankcase/block pressure through the oil filter housing, where as all the 058 style blocks have a plastic unit (which is offered in metal from some other older style block, maybe 16v?) that vents from right above the oil filter housing seen pictured below:
I am also under the impression that it is common for people to block off the hole the plastic "arm" on the breather goes to with a freeze plug and run a threaded adapter plate like the ABA/16v guys do to run it and the valve cover breathers to a catch can:
What does plugging the hole up with a freeze plug do? Would you not want to vent that as well as I'm sure VW put it there for a reason?
Help me learn!