Is it a performance mod? Hardly, but I'm not sure where else to put this.
Those of us driving lowly non-Spec.B Legacy GTs are stuck with the plain black pedals. I ordered the OEM WRX pedal pads only to find that the accelerator pedal is one solid piece of plastic, from the arm down. There is no rubber pad or separately-pivoting pedal (at least on the '08-'09).
So aside from the WRX clutch & brake pedal pads, I purchased a dead pedal from the dealer for $20. I then found that the 2012 WRX accelerator assembly is identical to the 2009 Legacy assembly. Two 12mm nuts removes the assembly, and the WRX assembly is plug & play.
Front of pedals:
Rear of pedals: