I have one exhaust manifold stud snapped off in each head. I think only one of them matters, as the one on the passenger side is the very front most stud, the one that is not used by headers.
The one on the driver's side has turned into an issue. One of the tricks I saw on the glorious internet was to drill a hole in the center of the stud and then hammer a torx bit into the hole. This sounded like fun, but I botched the operation by using a random cheap torx bit from my box of "junk" bits. I'm not sure why that seemed like a good idea. I was afraid to damage a nicer bit, but the reality is that you shouldn't even attempt something like this unless you are using a super-hardened bit that you know for sure isn't going to do what mine did.
Mine obviously snapped right off as soon as I tried to turn it, leaving me with a really cool star shape in the middle of this stud. The issue now is that I can't seem to drill this piece of torx bit with any drill bit that I own. I'm not sure what kind of drill bit would be required.
Several of you guys have cautioned me against disturbing the factory head gaskets, but I'm starting to get anxious about my ability to extract this stud.
I also have that same exhaust bolt broke off on the drivers side. I know it is easily extracted if you have the tools to do so-------BUT when i put my headers on over 10 years ago--taken them off at least 5 times, with out geting the broken bolt out-----my headers have NEVER leaked. But if I was in your shoes I would get it out.