If its that modified as to damage your brain you'd be better off changing the full system, not just the y-pipe.
Its not crazy loud, its just loud. I disagree though, i think most people do want something quite loud which matches the GTR as the type of car that it is. The most common modification on GTR's is the y-pipe for that reason.
Over here in Dubai you cant get banned from a track for it being too loud either