I have a 97 exhaust manifold with a broken stud. So I welded on a nut and applied heat to area around stud, still will not budge any body have any ideas ???? are these pressed in ???

 

They're threaded. Don't expand the material around the stud by heating it. Soak it over and over with penetrant for an extended period such as overnight. When you re-apply the penetrant, tap the stud. Get a longer tool to increase leverage and apply pressure fast and hard. Good luck with the removal.