u/Crow_caine

I recently bought my first car! A new-to-me '03 WRX! I'm trying to learn more about this car and how to take care of it, but I cannot figure out what this is. The previous owner did some modifications to the car (ej207 swap, intake, tune, stereo system, etc.). I haven't found what system this goes to, however. Is this a stock option, or an aftermarket piece?