One problem related to tank assembly has been reported for the 2003 Subaru Impreza Wrx. The most recently reported issues are listed below.
Occasionally my wrx smells like raw gas. Three times when I have been driving to mt. Lemon, up a very steep road, I have had a very strong (unbearable) gas smell enter the car. I took it into the dealer and was told that I am just "overfilling the tank," however, I never try to fill the tank beyond the automatic shutoff point on the gas pump. I have also smelled gas occasionally when driving but never as strong as when I drive to mt. Lemon.