Originally Posted by Frank in MD
So another interesting question is if you have a catch can, (even if you don't), should you also have an oil breather cap?
I think so. It allows fresh air into the crank case. However, you may have to get a your car tuned as this extra ventilation may allow un-metered air into the intake, and cause the computer to become confused. Confused computers will say "CEL".
Not sure if I got all the verbiage and articulated the answer correctly. But hope I am close. Tracy can probably confirm. I think it was he that informed me of that info, about fresh air circulating into the motor.