[terboboost]

You'll never feel any difference from adding a catch can (AOS), whether it is "good" or "bad". However, catch cans are for preventative care, in my opinion, to reduce oil fumes being introduced into the intake air, which effectively lowers knock resistance. No car "needs" a catch can. If a catch can is a "solution" to a problem, it is just band aid that will surely result in a negative end.

In addition, for maximum engine efficiency, a vaccum should be pulled on the crank case, especially under high load situations. Depending on engine setup, applying vaccum to crank case can yield over 50 hp, more realistically 1-5 hp (check out some high horsepower Supra's with downpipe venturi ports). This is why it is not a good idea to vent the catch can to the atmosphere, you aren't pulling any vaccum. This is also why it would be a bad idea to add a catch can that is too restrictive, which is what I assume the youtube video is getting at (I didn't watch it).

No experience with Mishimoto, but I highly recommend Chase Bay's catch can. No restriction, baffled, and uses a steel mesh filter.