Air/Oil separator any brand, preferably Perrin. Looking for used yet affordable.

 

I have a Grimmspeed AOS that I recently took off my car - you'll need all new hoses and connectors but the main unit that connects to the oil fill tube I'll sell for $80
it's red with a black center. GS AOS works great for street cars but if you track/autox your car, it will disappoint you.

 

can you tell me the pros and cons of AOS. And why is it good for street cars and bad for tack car? And differences with AOS and Oil catch can?

 

no, but you can look it up. :-)

The short answer is that the GS AOS doesn't work well in extreme conditions like an open road course & autocross.

I know this from personal experience, but you will find that many others have discovered this as well. It works, but it isn't perfect. If you want the most recommended AOS, it's IAG's AOS. I am using a Crawford AOS now because I got it really cheap from a group buy.

 

My Grimmspeed couldn't even effectively function during autox. Replacing with IAG AOS.
To OP, if you don't know the answers to the questions you have asked you probably should just leave your factory PCV system alone. Why do you think you need one?