not necessarily ... sometimes it has to do with the type of material that the bolt is made of vs the type of material that the manifold is made of. both myself and a friend used to run the ceramic coated inline pro manifold, and both of us had constant problems with bolts breaking or bolt heads breaking. we tried heat treated, high grade steel, etc. we just started keeping them on hand in the car.

we are thinking maybe the heat expansion and shrinkage properties of the two types of material cause this to happen.