I had problems with my 2007
I had problems with my 2007 Impreza - head gasket. I did research and found Subaru was on their fourth version of head gaskets for the Impreza.
I had bought five Subarus at the time and got onto head office and told them they had sold me an inferior product - which was true.
They paid for the repair - replacements of head gaskets - $1600.00.
Pressure them - don't give up.