Very stubborn studs..

All 8 exhaust studs have been drilled out with a 5mm drill bit. None of the remainng studs are willing to let go.. Neither penetrating oil or a bit of heat will do the trick. Next stage will be a 6 and finally a 8mm drill bit. If the 8mm is needed than a full Helicoil treatment with tapping and thread replacement will be necessary. More soon!