Found out about the wax trick somewhere on other forums. I used a propane torch to heat up the cast surrounding the stud, let it cool for a minute then rubbed a wax candle onto the stud and let it drool down. Of course it fizzed away for a bit. Then using the double nuts I simply unwound the stud out of the manifold. And yes, I think it migrates into the threads once the dissimilar metals are released from one another due to the heating process.
