One thing that Subaru does is they reuse the same plugs but for different purposes. These fog light plugs in older model cars are used as different plugs in newer models. If you’re using these plugs for something else, make sure to check the keyways to ensure they are the correct plug.
A common fog light upgrade is for 99-01 RS cars to 02-03 fog lights. The 99-01 RS fog lights are difficult to find so instead of the hassle you could use 02-03 fog lights with the plugs below. You would just splice in the new plug pigtail and be good to go.
Click on the picture below to see more about the plugs listed.
1993-2001 Impreza Fog Light
2002-2003 Impreza Fog Light
2004-2007 Impreza Fog Light