Bolt-on low restriction muffler which I fitted to my 1994 Legacy a year or 2 back when I was playing around to see if I could squeeze a bit more power out of the engine. Seemed to make a difference, but the missus hated the sound of it - not really loud, just different - so I had to put the original back (she drives it more than I do so seemed reasonable)
Cost over $300 when I bought it, happy to let it go for $150 OBO.
Email me if you're interested & we can take it from there.
Chris