it's hot there. they rust unless you use stainless which is to soft to hold in my opinion.
you can get a pcm manifold set from skidim with 16 bolts, all gaskets(put them in right) and the riser bolts for 70 bucks or so.
never-sieze on the threads will keep you from snapping the head off when it comes time to remove them.
yes, i have broken one of those allen headed buggers. it was overtorqued by the po.