which stud is it (drivers/pass. side? front 2nd, 3rd, back?) im assuming you've already soaked it down in some penetrating oil like PB and you've tried sticking a set of vice grips on it to try and turn it out? also, is there any of the stud protruding from the hole? if so, you may be able to heat it up and twist it out. if there is enough protruding out, you can have a nut welded to it and then back it off. if the stud is broken off in the head, you'll be pulling the head to fix it:imo you may get lucky and be able to get it out with an easy-out solely depending on which stud it is. that sucks to hear. i used two cans of PB when removing my manifolds. i soaked the bolts down the night before pulling the manifolds. that morning i resoaked them and while backing the bolts out, i turned them left and right a few times in order to make sure that they broke free from the threads inside the heads.