It's just a general site for Celica drivers to show off their dyno results. I don't know if it's just TRD mufflers, or the full cat-back. My guess would be for the Celica GT, it was just the muffler since their doesn't seem to be a huge loss of low end power. For the GT-S, he probably went for the full cat-back since at rpms under 4000, he lost as much as 10 hp at the wheels. Like you said, its up to you whether you could deal with that loss of low end power. For me driving around normally, I rarely go above 2800 rpms, even under hard acceleration. To hit 3000+ means you got to push the pedal all the way and hit wide open throttle. Usually rpms of 2200-2800 produce more than enough power for me to pull along quickly around town without making my engine rev out and start getting loud. I probably couldn't deal with a loss of power at the range.
The basic point I was trying to show is that people throw away hundreds of dollars on these stupid aftermarket systems like TRD exhaust, headers, or CAI setups which brag to you that you'll see gains of 10, 15, or even 20 hp. In the end, even with all those things combined that Celica GT saw a general gain of only 1 hp! Personally, I would just save up the money from these ricer products for something that returns much more visible gains like a turbo kit or supercharger.
