I think the oil seperator, or oil trap, might be what your thinking of, located under the intake manifold. Positive pressure vapors from the crankcase are vented through there, and any liquid phase oil drops out and is supposed to drain back into the pan I believe. The vapors then go through the flame trap, and back into the engine air intake stream, right before the throttle body. The more common ailment is a clogged flame trap, and cleaning that is far easier than cleaning the oil seperator, the intake manifold has to come off to get at that. Still not a really complex job, just more so than cleaning the flame trap, which will take you about 10 minutes with a screwdriver and maybe a pair of pliers. Both are common operations though.