Stock.
But in all seriousness I wouldn’t think a Catback exhaust would be illegal unless it’s ridiculously loud, the issue is removing the cats that make it illegal. Seeing it’s a Catback it should be all good. I have an STI axle back, happy with the sound and looks good IMO. There isn’t much to be gained between either an axle back or Catback powerwise I would of thought, so if you’re just after looks and sound, maybe an axle back is good enough and you save some $$$ too. If you’re after more power, a header and a tune is the way to go but then it would likely be illegal.
Invidia Q300 Catback is a pretty good choice IMO.
STI axle back