1. It intercepts the blowby from being blown back into the intake.
2. It stops oil from accumulating in you intercooler and turning into sludge, your chargepipe, Tmap, and back on your valves.
3. None that I know of, I don't know how it could leak on someones spark plugs?
4. I would have to guess the Mckinney one right now. I have the RR and it works good enough, emptied it out ...



