If it was the dip stick - wow....however, this may be a sign of something else.

The engine cavity. where the oil is - should be under a negative pressure provided by the vacuum line into the SC inlet (post throttle). This is to recycle oil back to the combustion chambers. Some add "catch cans" to separate this out so it doesn't go through the engine.

When you had the covers off, check to see if anyone knows if the galleries in the Left hand bank cover where all nice and clean/cleaned. If they are blocked - this vacuum may be hindered/non existent.