A common oil leak on your car is the oil pump drive o-ring. It's essentially a distributor with the top cut off that is located in the center of the block and can be seen (barely) under the throttle body. It is a 2 minute job to replace while you have the intake off replacing the intake gaskets, and requires removal of the upper pleunum and throttle body to replace if not done when the intake is off. It will leak oil down the side of the block and will appear to be a rear main or oil pan leak to someone not familiar with this engine.