Our friends at TurboXS haven't had a specific exhaust for the STI before now, so we initially installed the single-tip system indented for the WRX hatchback. That fit fine, sounded great, and was nice and light, but especially after we fitted up the STI accessory rear garnish bits, it always seemed like the car was missing something over on the left side of the rear valence.
I thought the sound would be a lot quieter than the single-tip system (after all, the muffler looks about three times as big), but it sounds very similar to the old system. It might be a tiny bit deeper in tone, but the volume level didn't seem to change. The look is great. Some systems for the STI have a pronounced "drain pipe" that hangs down just before entering the muffler, but the TurboXS system tucks nice and close up to the body.
The new quad-tip TurboXS system for STI hatchbacks will be available for purchase on our web site in the near future.