IMO, the easiest solution (cheapest too) would be to throw a few thick washers on there, and see if you can get it tight enough with the bolt positioned on a better section of the stud.
otherwise, you can always replace the stud. i'm not familiar with that particular manifold, so i don't know if the stud is set, or threaded in, but worst case scenario, you can cut it off, drill it out, and then tap it with new threads.
you can pick up a new stud kit at pretty much any auto parts store, if you don't want to piece it together yourself.
Good luck
