Iv see a good many threads on peoppe asking how to extract broken exhaust manifold studs or bolts out that break in the cylinder head or flush. I ran into this problem last night and usually weld nuts to them to extract but was having a hard time for some reason.
Last time I used a actual easy out or extractor it broke off in the stud and I was really screwed.
Now this might have been covered before but I didn't see anything after a quick search so for those who have not ever tried this I found a quick easy fix that works with a little TORX bit.
I took a punch and a hammer, tapped the center of the stud a few times to get a start for my drill bit. I can't remember exactly what size is used but I will post In comments later on because it's still on the cart.
So I drilled down into the center of the stud about 1/4 of an inch maybe less. I then took a Torx bit and hit it down into the center hole i drilled on the stud. not hard but enough to know it was in there.
little bit of back and forth and some wd40/pb blaster and it came right out. Torx bit was still perfect. the studs are softer then a Harbor freight 1/4 torx so it seats itself into the stud almost perfect. it might take a couple of tries. I'll post up the drill bit size and torx because the combination worked perfect for me.
if you didn't know now you do, if you did this will help other that are stuck and struggling. I did it with the head off the engine but this will work in car as well. drill straight!