Sorry I've been away for a while. I've been going through some pretty big changes. I probably won't be spending as much time here as I used to, but I'm not going anywhere. I'll explain later...
Your valve cover breather is supposed to be plumbed into your intake pre-turbo so it can pull vacuum when you're off-boost. What a catch can does is collect oil from the vapor and prevent it from routing back into the intake... before the turbo. Yes, they can be vented to atmosphere, but since vacuum assists the PCV in its operation, I don't really know what the benefit of doing that would be.
On a N/A car, this breather can connect anywhere on the intake pipe. On a boosted car, it needs to be on the intake pipe before the turbo.
Before you assume that the oil IS coming from the valve cover breather, remember that there are 6 places that you could be burning oil from on your engine. I think the valve cover breather is not a likely candidate, but with the way you have it set up (vented) a catch can won't help with your oil burning, it will just look pretty, and will keep you from getting oil blow-by on the outside of your engine like you do now.
1. Bad PCV valve
2. EGR valve (I'm not familiar with the B18's setup).
3. Valve seals
4. Head Gasket
5. Rings
6. TURBO SHAFT SEALS
In reference to #6... What's your peak oil pressure? I know you have a gauge. You have a T3 hybrid, right? Those things are REAL picky about oil pressure. You can never exceed 60 PSI or the seals will blow. A boost leak test will also indicate whether or not you have bad turbo shaft seals. The pressure will leak slowly, and you'll hear your turbo hissing from the exhaust.
Here is why I said to take apart your intake pipes and why you should examine them...
If you see wet oil streaked from the PCV breather hose on your intake pipe, then you probably need to check your PCV valve. If it's working properly, then you CAN benefit from using a catch can. Here are the instructions FOR A DSM (but the Honda principle is the same).
http://www.tgilmore.com/talon/catchcan.html
If you see wet oil pooled in your intake pipes, intercooler, and throttle body inlet... and your PCV valve is okay, then it's your turbo's shaft seals. It either needs to be rebuilt, or you need to start saving money for your next upgrade.
If your intake manifold is crusty and blackened with large chunky carbon deposits, block off your stinkin' EGR valve and call it a day. (but leave any vacuum or electrical connectors in place)
If you pull your plugs, and they're oil fouled, but none of the above are a problem, you'll need to do a compression test and leak down test to determine whether it's the valve seals, head gasket or the rings.