i had an exhaust leak coming from the exhaust manifold to head gasket. was a slight sound of air escaping, and by 1 week later my car was as loud as a tractor. couldnt drive it and yes i did lose performance very noticably. however urs might be tiny and maybe from the turbo/manifold seal
btw cost me $350 to get 5 studs fixed with all new sleeves/inserts and the like by a professional thread repairer. he said it was the 2nd hardest job he has ever done. whoever changed the manifold before completely destroyed all the bolts/threads etc..