i ended up drillin gthem out form m6 to m8, re tapping them to m8x1.5pitch,
and fitting new studs with loads of copperslip on. you will have to drill 2 of the holes in teh manifold though as they are a very tight snug fit at m8, literally just pop a m9 drill through them. and i used new stainless nuts with again loads of copperslip on them. the intense heat must fook the facoty ones up as there will be no copperslip on them, only studlock, which is great for fit and forget, but then when u need to take it off to have the head skimmed etc, it s right pain as they either have alredy been stripped by someone else or they wont undo and strip