I can't answer, not sure.. rave page if it helps...Thanks @kermit_rr. In the end with the amount of work to remove the manifold and potential of more broken studs/bolts I decided to drill the stud out in situ which was a pita but all done now. I don't have a tap set and can't seem to find a m10x5mm tap on line. Do you know if Is there any reason I can't use a nut and bolt in place of a stud assuming it can be torqued to the right setting? The other two connections would be studs?