I had an exhaust stud break on my old xb9sx. Took it to a machinist who tig welded a hex head bolt onto it, and was then able to wrench it out. However it took him FIVE attempts to do this since the first 4 times the bolt broke off when twisting it. He was just about to give up on the 5th time, and said he'd never had to do it 5 times.