crank case ventilation. Supposed to be connected to the intake, but lots of people just put that little filter on there.

 

is it really necessary? i just put a 22re in my 4runner and i have nothing there just air blows out!

 

Having nothing there is really like running without an oil cap, you've opened the top end and your oil system to what ever funk wants to get in.

The little filters are a nice easy way out when you're doing something like The ISR mod, but even then your still exposed to getting water in your engine, I'd do something about it post hast.

 

Yes it is necessary, otherwise you would have a massive vaccume leak

 

yes. quite necessary, either having it hooked up to the intake or have a filter on it like you do there. I bet your rig would run better with a hose attaching it to the intake.