I have successfully and unsuccessfully used easy outs. I have gone to the tap in kind instead of the cork screw variety, but a left hand drill will usually do the trick.

I had the problem on my 96. The bolt just broke off one day flush with the outer surface of the manifold, about 2" from the cylinder head, just broke, never been touched from ford. I thought I will just remove the other bolts with my impact, and they all came out, but there was no room to get the manifold off the broken bolt, manifold hit the frame, I had to jack the engine up high enough to get the manifold past the frame so that is why you do not leave it there and use it for a stud.

I thought "this will be easy, I am lucky today." I put a stud extractor on the case hardened grade 8 bolt and went to turning, and it snapped off right flush at the head. I drilled it and easy outed it, broke a drill bit, drilled some more, got to the threads on one side, broke a bit, then went and baught abrasives and carbide cutters for my die grinder.

I burned up 2 abrasives then went to the carbide, cut and cut some more, metal was flying.

I swore and I sweat!! Finally the shard that was left in there I could turn with pliers, it would not extract though, so I got my left hand bits back out and about 15 seconds later it was out. Now it sets in the shop on the shelf under the "wall of war"

Brute force and ignorance sometimes is the only way.