2006 9-3 spark plugs knee deep in oil
 

I changed my plugs about 5000 miles ago.....now I have a low rpm hesitation and she feels sluggish and low on power. So I swapped a coil cuz i had one left I had not replaced yet and when I pulled the coil off the plug was sitting in a half inch of oil. Pulled the plug and it was coated in oil. Checked the others and they were all the same.....knee deep in oil.
So I need to change the plugs again. Where is the oil coming from? Could it be coming thru the threads of the plugs? Could I not have tightened them enough the last time I changed the plugs? When i snug the plugs they feel like they cant go in any farther and I do not want to snap one off.
She has 105k and she has the 2.0T.

Any ideas?