Originally Posted by aserr
As a final update, after about 2000 miles and 3 months, the CEL has not returned and the car idles much more smoothly.
I don't know what else to say, the valve adjustment appears to have solved the problem and despite the cost, I will probably stick with the Subaru branded 5w-30 synthetic for all future oil changes.
With regard to the cost of the oil change charged by the dealer, I'm not going to bother hassling them about it. Not that 100 bucks is chump change, but I have better things to do with my life.
We've had a couple of wrx's like this. The guy who had the first one lost his ass on it though. Both ended up being valve adjustments and never came back.