thats the rear valve cover. im guessing that if its in any way associated to the dpfe sensor i just pulled (so corroded it snapped off in the hose) maybe the exhaust leak burned that hole. no wonder oil level was low when i got it! my car has been in the garage since monday & this is the 1st time i could visibly notice a leak. it was a very small puddle basically under where the firewall sits. but the dead giveaway was came up when i moved the coil pack & dpfe. everything in vicinity of that hole was/is coated in oil!