A "race" header is generally one that is very high flowing, with large runners and a big collector. They usually replace the cat and end right where a standard cat-back exhaust would start. Since the Celica's B-pipe goes all the way from the end of the header to the rear axle, a special "race" header would have to replace the stock exhaust manifold and the entire B-pipe and would extend from the back of the head all the way to the muffler.
If you want to simulate a "race" header like those available for the RSX and most other Hondas, you'd have to buy a Trial or TRD
header and the Kazuma and mate them together. It would basically be the same thing, but it wouldn't look as nice.