ME Wagner PCV – does it work?

Wondering if anyone has had luck with this adjustable PCV from ME Wagner? I have a 408 Stroker with a Holley EFI Sniper. I put a regular PCV and attached it to the port on intake manifold but it affected the idol.

Also, I'm putting on Mopar Performance valve covers (cast aluminum), cast iron heads. Any suggestions on the best gasket to use? Rubber coated fiber or silicone with metal core?

Thanks!