A slight knocking or ticking sound is VERY common on all Subaru's after a cold start. As long as it goes away when the engine is warm you'll be fine. Not that long ago Subaru sent out a memo basically saying "a slight ticking sound that gradually goes away as the engine warms and is barely noticeable from inside the car is normal..."....or something along those lines.



As previously mentioned you may also have a hydraulic lifter that is misbehaving when cold. Either way I'm sure your engine is fine.




Dave