A few times in the recent past (it doesn't happen all of the time), I've had a situation where I'd coldstart my 2000 OBW in the morning and it's idle speed would be 3000rpm! Now this has happened a couple of times despite the fact that it was sitting in a heated garage overnight. It also happened another time while it was sitting outside in relatively mild weather (for this time in Canada) of just around 0 Celcius. In the past I've seen Subaru's variable fast idle speeds never went over 1500 or 2000rpm, even in the worst of conditions (i.e. sitting outside at
-20C or lower). I changed the air filter since it was dirty, but it's happened a couple of times since the air filter change too.
During the times when it's idling at 3000rpm it's keeps tending to want to keep at that speed for what must be 5 minutes, even while driving. So when shifting gears (i.e. 5MT), you have the unusual situation where the engine speeds up between shifts rather than slows down.
Computer problems? Sensors?
Yousuf Khan