[quote=apkano]
3. Interference fit.....it was installed with one part hot and the other cold...when the temperatures return to normal the parts expand to make the stud fit tightly in place. Again. it could require considerable force to try to remove.
quote]
You mean shrink. I assume when you say cold you mean room temperature. This is a car part and not the space shuttle so it would be just pressed in, if it is tight that is.

I would say its welded in place as the material is too thin for a workable press fit so it would turn when the nut was tightened.
Looks like it will have to be drilled out.