There is a member here (yellow 07 ZX3, runs 12.7 with N02. "why hate on the 2.0?") , I forget his name. Anyway, he showed a dyno after all those mods except the 2.3 head and he had 160+ whp. I would venture a guess that with the 2.3 head he could have maybe been at 170. This is PEAK hp at a high rpm. You are better off with the full D23 that is in your ST, honestly, because you have the tq throughout the powerband. His is made for the track.
05 ZX3: Steeda intake, 67mm TB, custom 2.5 Magnaflow exhaust, Tom's Tune.
New: 04 SVT : K&N panel filter, 3 performance motor mounts, Taylor wires, orp, 67mm TB, Tom's Tune.