I had that happen to me this week. my code was P0483 which was cooling fan rationality check, but 3 days later it just went off on its own. hopefully its just a faulty code. its seems odd but i have a 06 wrx too at about 46k miles. did it happen while your car was idling?
I have 06 wrx tr..same thing here. car seemed like as I was revving up to 4k...no turbo power. Called the dealer he said disconnect the battery. I assume to clear out any stuck bits in the ECU. that fixed it. took the car out for a spin and everything seems ok. I'll repost after a few days of driving.