Cdanders, there are a few things that it could be. A good guess would be the air flow meter since 99 percent of the time they do not throw a code when they go bad. Also, does it act abnormally when just idling or only when you attempt to accelerate as you mentioned.
Knock sensors can cause the car to stumble and hesitate when they are bad but they usually trigger the check engine light. Same goes for the throttle position sensor. When was the last time you changed you plugs(what kind) and wires? Neither of which will cause a check engine light to come on( in the 1st gen Legacys anyway) but both can make a Subaru act like it's posessed, especially bad wires.
[This message has been edited by Shik (edited September 26, 2000).]