PCV System Question
teke184 has got it right. On systems capped off would only vent excess crankcase pressure, but would not do anything to flush out the caustic combustion byproducts, moisture, and unburnt fuel. For a turbo (or supercharged application) you will need to still use the intake manifold as a vacuum source (the nipple on the pass side of the intake snout) but will need a one-way check valve inline to prevent back-flow when under boost (as the intake changes from a negative atmosphere to a postive one). You run a line from the valley cover (in the LS6 valley) or in the case of a LS1, the rear of both valve covers, to the inlet of a good oil seperating catch can that is NOT vented, and from the catch can outlet to the intake manifold vacuum source with a check valve inline. This provides a proper flowing system for non-boost. Then, you would run a line from the intake air filter for the turbo with another checkvalve in-line so air can flow from the filter, but not out to it....this would Tee into the outlet line of the catch can so that it provides the suction/vacuum while under boost. Then for filtered fresh make-up air for the crankcase, put a breathered oil fill cap. This set-up allows a constant pull on the crankcase to evac the nasty crap from the crankcase, relieves pressure, and provides a good unrestricted source of filtered fresh air to be pulled through the crankcase. 
get an ls6 valley cover, then you just have the pcv hose run from the intake manifold to the nipple right under it.
http://www.ls1howto.com/index.php?article=18
http://www.ls1howto.com/index.php?article=18
A hose from the P/S valve cover rear tube to the D/S plastic insert will aid in passing the filtered fresh air provided by the TB.
Another option, as someone else mentioned, is to get an LS6 style valley cover. There is also an updated (2004+ LS6) valley cover that doesn't even need a PCV valve, it has a newer style metering orfice. They work much better than the old LS1 PCV systems, make for a much cleaner design (less hoses and crap) and cut down on PCV related oil consumption.
As for people considering deleting your PCV and running breathers, take it from someone who tried it, and don't waste your time. You end up killing your oil (I had yellow sludge buildup in my oil cap from moisture) and the filters quickly get oil soaked and smell really bad. Every time you pull up to a stop with the windows down you get the stench of crankcase vapors right in your face. The PCV keeps the inside of your engine much cleaner, without it you get buildup of acidic contaminants in the crankcase that ruin the life of your oil.
If you don't like your PCV system and want to go to breathers, spend the $56 and get the 2004+ LS6 valley cover, part # 12577927. You can even run a catch can with it if you'd like. Thats what I converted to, and its been working nicely for me.
