Ive seen a very similar problem,it was happening for months,it would just cut out around certain corners,no one could find what was happening.We tracked it down to being the main + power wire that goes from the battery,to the bolt that goes into the bottom of the middle fusible link,the fusible links are located down in front of the fuse box in the engine bay.Just follow the wires from the positive battery terminal if you cant find it.Theres a little black plastic door that pulls open so you can access this bolt,the bolt has to be removed if you want to replace the middle fusible link,and what had happened was the battery was moving around slightly from side to side when cornering,which was moving this power wire,this movement eventually caused the join where the wire has the connector crimped to it, to pull out of the connector, but it was making bad contact for ages and stopping the car, before it finally broke completely.If yours is cutting out,check the battery for any sideways movement,if there is,see if it moves this wire,and check the crimped connection behind the little plastic door.