The Air/Oil Separator or Catch Can solves a simple problem from the manufacturer; it transfers the oil into the catch can not the intake. This not only keeps the vehicle within specs of smog but keeps the oil from coating the tops of the pistons. We all know what that does to any tune you have; it causes detonation, a very bad thing for engines.
Detonation often leads to serious motor damage or even a blown motor. This Air Oil Separator / Catch Can will not only help protect your motor but it will add that extra little spice you're looking for in the engine bay.