Use caution... the envalve website made my firewall go ape s&*$....
Here is a thread about it on LS1 tech
Hmm? Envalve eliminates excess blow by? - LS1TECH
IMO I don't see how a PCV valve is going to improve fuel economy unless the one it is replacing is clogged in which case you can save $50 and replace the valve with an OEM replacement.