Any blockage in the pipe can make turbo temperatures skyrocket.
Most likely, you loaded it with coolant when the gasket went boom.
Very typical to see this happen post coolant-passing head gaskets.
I would gut the freaking thing and cure it forever. They cause more trouble than they are worth, once you add up all the fuel burned into the air it takes to build/maintain and repair them. Fools errand.
WATCH OUT about a used turbo from a spoiled engine.
The same oil passes through the turbo. If the motor popped, it usually compromised the turbo along with it. It won’t show up right away…and no one will sell a turbo off a good engine…they go as a unit, together.
Look into a local turbo rebuilder for a bargain. They will be your best bet.