It sounds like you either have a head gasket failure or have damaged a piston. You really should get a pressure test on each cylinder to find out what the cause is. Also get the header tank pressure tested for a head gasket failure. If a spark plug has burnt out the cylinder is running too hot and causing damage to the electrode. That may also mean damage to the piston, bore or even the block itself in worst case scenarios. I would limit driving the car and consider getting the car towed to RTech when its booked in for the map. Hope you get it sorted mate.