I have a turbo kit on a 2006 5.3 and it is a front mount. I original had filters on both valve covers for the crankcase venting but I did not feel comfortable with it so I ran passenger side to fresh air via air filter inlet of turbo and the passenger side I believe needs a one way valve such as the on APS uses on there kits to keep from boosting crankcase and I also don't understand why they say to drill the orifice in the valve cover to 1/4", and also where do you get the check valve?

 

Check valves off of an Evo VIII are great to use if you're using rubber vacuum lines. I think they run around $15 at auto part stores.

 

link??

 

Here's a picture of what I'm talking about. A quick google search should yield a website where you can pick them up. I've used them on my non GM turbo builds and they work like a charm.

 

these are what he is talking about. http://www.boombaracing.com/cv.html