I would say head gasket gone.
Have a very good look around number four, exhaust side just above rear core plug this is usually where they go, as they cook on this pot being the hottest AND the weakest.
This is due to crap design of the cooling system, and not enough water circulation.
When you get the head off if it has any more than bout 50,000 you will most likely find the guides and exhaust valves are shot as well, seats will defo be buggered.
Use YBO611 new h/gasket, ARP stud & NUT kit just for a bit of security, I always do a final torque to 120 lb ft, regardless when doing these.
White marks on the turbo is nothing at all to worry about, it is merely water that has boiled on there, could be from washing the engine bay etc when hot.
It is a little bit of a ledge there so water collects there when engine cools overnight, then boils when you start that nasty hot turbo up!!
tabetha