Sorry to rehash this old thread like this, but I thought this might be interesting to some people.

Here's what a poorly-implemented PCV can do. This is the upper intake manifold from a 2000 V6 Mustang, which has an extremely over-active PCV system (99 and 2000 were very bad, Ford corrected the issue mid-year in 2000). It pulls significant amounts of vapor into the intake, and deposits oil sludge in the #3 and #6 runners.

Here's the bottom of upper manifold.


Here's a closeup of the #6 long runner. Check out all that wonderful black tar the engine was choking on.


The #6 plug actually wasn't fouled too badly. Suffice it to say I will be removing the PCV system from this car shortly.

Hondas don't much have to worry about this.