EZGO exhaust stud broken

[mninni]

I have a 2005 gas ezgo but all of the documentation shows the engine might be a different year. The muffler is a 74929G01. I need to replace the muffler and the first bolt I tried to remove broke off. It is a stud into the engine. I was more careful with the other stud, and the 2 support bolts so they didn't break off. The documentation I found shows the nut (for the exhaust stud) is an M6. I also have an engine manual that shows an M8 bolt. Regardless, I'll measure the good one to see what size it is. The question I have is how difficult is it to drill out the old stud and re-tap for a new one? Is this going into an exhaust manifold or into the engine? It's hard to see straight on into this for centering a drill on the old stud. Before I mess this up, has anyone drilled out a stud? What material is the exhaust manifold? I've been soaking the best I can with liquid wrench to try to break down the rust.
Thanks.

[CP241]

Your 2005 should be an MCI engine... the exhaust/muffler bolts straight into the head. The older engines had a cast iron exhaust manifold between the head and the muffler.

Your best bet would be to carefully drill it out and install a helicoil or time sert. Then a new stud or a bolt into that with a lock washer. And make sure the bolt on the bottom frame rail is secure to the muffler, this mount supports the muffler. If you forget that one it will strip the new bolts out of the head too.