The exhaust connects to the CYLINDER.The exhaust bolts do not go all the way through. Leave it together, and see what you can do with it the way it is. If you take it apart, you might crack a piston ring or two when you put it back together. The STUD bolt for the HI TORQUE - CYLINDER is [m6 x 18] and is made of steal. You need to find out if there is any of it left to grab, if not you will have to center punch it and drill it out. Easy out is an opthion. I never had an easy out work for me. Sear has a tool like an easy out, but they claim it is better, so see if that tool may help you.If you tap it, you will want to use a bottom tap.