I've had 4 Subies over 18 yrs and none of them have pulled. I can take my hands off the wheel and they will go straight.
Try increasing the tire pressure slightly on the front tire on the side that it is pulling towards.
Originally posted by Roy Lin
I was hit in the rear at 5 mph once... do you think it might be frame issues?
No; a 5 mph hit should not affect the frame.