This last weekend, we had a 3 vehicles with idle issues that were traced to incorrect catch can installation or missing PCV valves. These cars had aftermarket intake manifolds, throttle bodies, and air filter assemblies so someone else made the mistakes which we caught.
The LS1, LS6, and LS2/LS3 all have different PCV systems. If they are modified such as removing the PCV valve, capped vent lines, it can mess up the idle air flow or cause excessive oil consumption by pushing oil to enter the intake manifold.
Just a heads up to everyone that tunes on a regular basis, check the PCV and related vent lines to make sure they are hooked up and are working properly.
Here is a good explanation of the various PCV systems.
PCV SYSTEMS