The big HP gain is not from the exhaust, but from the test pipe.

Check out my plots from a tune session with the 63mm T1R/Test Pipe, Toda header, and AEM EMS.


***********NOTE*********
SO PLEASE, DONT RATTLE OFF "184HP IS LOW FOR AN S2000"
THIS WAS TUNED ON A MUSTANG CHASSIS DYNOMETER, WHICH YIELDS LOWER NUMBERS THAN A DYNOJET; REMEMBER, WE WERE NOT SHOOTING FOR BIG NUMBERS. USABLE MIDRANGE POWER WAS THE KEY HERE.

Smooth, usable power band > Big Numbers

http://www.p1auto.com/jack/s2k/s2kexhaust.htm