My CEL is on permanently after a firm drive through the country side this afternoon. I am not decatted and have made no changes to the car while owning it.

Anyone have any ideas what this could be?
What should i expect to pay when i go to subaru dealer?

 

From your "view my subaru" its a bugeye so will need plugging into diagnostics.

Some local garages may have the cable to read the ECU fault codes without going to a dealer or specialist. Some dealers will diagnose for free, others charge - I've heard up to £50 quoted in UK so best thing is to give them a ring.

You have an STi so no EGT sensor, so possibly O2(lambda) sensor after a good blast.

 

Yes its a bugeye sti type uk. Will have to get the dealer to have a look. They are very reasonable so i hope they don't throw the hand in.