It seems pointless to connect a vented can to the intake, unless I am missing something about its design that prevents the intake just sucking in air directly from the filter. In fact, one should definitely not connect a vented can after the MAF, and even before the MAF I would rather not take chances of the MAF element getting gunk on it, in case blow-by or droplets still make their way through the can.
If you want a vented can, for example if you are running an open turbo without an intake, you only plumb it to the valve cover. For this application, it is not necessary for the can to be baffled, as it only acts as something to catch whatever the motor pukes out from ruining mother Earth.
I would assume that a non-vented can connected between the turbo and MAF (or between the throttle body and MAF on an NA motor) would be the most effective, because it would serve a dual purpose of not only trapping blow-by, but also creating negative pressure in the head directly proportional to the amount of load the motor is under, thus (in theory at least) helping fight undesirable conditions such as head lift.
Personally, I am not going to run a catch can because I know I would never empty it. I will just let my motor suck in its own filth.
