I'm pretty sure the pic in that link isn't specifically for the Celica. The way the pipe is bent in the picture, it wouldn't fit. The invidia is axleback, not catback, but it says catback on the box. Like Immo said, it WAS way loud for me too. I think after the ECU adjusted, it wasn't as loud anymore. Now it makes a really nice sound, although a little loud at certain rpms. When I first put it on it was more than I could handle. I was getting headaches driving my car lol. But it's all good now.
I'm not sure about dB legality, but it comes with a silencer that makes it pretty quiet. If you want a clip, just pm me and I'll send it to you, because I don't know how to put it on this site.