I have the angled breather, the one that sits level, on the D/S as well, still getting a lot of oil out of that side. Pretty sure boost is getting by the PVC and into the crankcase, have an ACDelco PVC on order as well as a check valve to put in before the PCV to make sure zero boost gets into the crankcase.
Even without boost getting by the the PVC, oil can still pool on the rockers and get into the breathers, especially the P/S one on the stock valve covers. I'm leaning towards picking up some new valve covers so I can have 2 breathers mounted on the top of the covers. Probably the GN1's, might also put in a remote breather system.