Hmm I've never heard of the Type-S leaking. I know a ton of people that go with that BOV and not a single one has problems. Two of them actually pressure tested their system to 25psi and there was not a single leak.


To vent, or not to vent. That is the question. (which has a really simple answer. Do NOT vent.)

Here is the deal, and this is the last time I am going to type this.


The air sensor measures the incoming air before it gets to the turbo. It then sends that measurement to the ECU so it knows how much fuel to add to the air/fuel mixture inside the cylinders.
When the BOV goes off, it shoots that air, which was already measured, back into the system AFTER the air sensor. This keeps the ECU and engine happy because it does not lose the measured air.

Now, if you do not let the BOV vent the air back into the intake, that measured air leaves the system. The problem here, is that the ECU has already accounted for that amount of air and dumped the correct amount of fuel into the engine to keep the air/fuel ratio happy. Since the measured air is no longer there, too much fuel goes into the engine and causes a very rich situation. This hinders performance, causes the engine to stumble, and is just overall bad.

Get it? :)