It doesn't meter the vacuum properly and has caused BLM issues on some cars; but, the factory PCV doesn't restrict boost pressure as it should and carnkcase pressure pushes oil everywhere. Sounds to me like you need both. The RJC crackes open at a mild vacuum so the factory PCV will do it's job, and when boost hits, then the RJC valve hits and hopefully keeps the boost where it belongs. Kirban sells the RJC valve and another brand valve that is to be used with the factory PCV. I'm going to try using a new factory PCV as well as one of the PCV checkvalves available, probably the RJC as I've had good luck with their other products, but I've had good luck with anything from Kirban too, so do as you will...just my 2 cents. I'll report back after I start leaning on her this Spring.