96 jetta gets "engine smell' in cabin

I have a 96 Jetta with 2.0 motor. If you idle the car, a smell similar to crankcase comes in through the vents. car has 150K on it, I have owned it for 11 years. could it be PCV valve, MAS, I have no clue. I replaced the long skinny hard plastic pipe on the front of the engine about a year ago. Sorry I don't remember what that piipe was called. Any help would be appreciated. Thanks.

The outside air intake is under the cowl inside the engine compartment. If there is any oil on the engine, it will burn off and the smell will be sucked inside. When you're moving, the burnt oil is blown out of the engine compartment.
If you get engine cleaner and clean it off really well and make sure your valve cover gaskets aren't leaking it will help.
Check your exhaust for leaks to be safe!

Doug,

Thanks for the reply. I replaced the breather hose about a year ago, since it was cracked, but now I have that same smell. It is more of a crankcase smell, and I am going to follow your advice, and see if a cleaner engine will improve the situation. I do have a bit of oil on motor due to bad valve cover gasket, so perhaps that will help. THANKS!