broken exhaust manifold stud

To add to this. After welding the nut on good, heat it all up good and hot right before trying to back it out. Heat loosens up the corrosion that causes bolts to break.

 

I've removed my share of broken exhaust studs. My tips and suggestions.
I've always drill all the way through the stud and spray penetrating oil in the hole before the ez-out goes in.
I prefer the square cut ez-out over the fluted style.
Make sure you get a good center punch mark before you attempt to drill.
I screw a good stud in an adjacent hole it will give you a reference to help keep you on the straight and narrow.
Cat says to torque the studs. I don't, I double nut the stud just to make sure it's seated.
PDI sells a better sleave it's one piece unlike Cats which are two and can separate.
Unless it's a lug nut and stud put anti-seize on it.

 

Torq's bits also work well it the hole is the correct size.

 

Like this after someone else broke off an easy out.

 

if a pair of vice grips does not get them out i always go straight to welding a nut on, then if still stubborn i use a impact with very quick bursts of the trigger has always worked very well for me, if they are below the surface i just build up tack welds till i get it high enough to stick a nut over and weld it to the tack welds.