here's a short rundown:
1. apexi ws (world sport)
-made for daily driving
-focuses on mid-range torque
-cat-back style
-for gts (not gt) celicas
2. apexi n-1
-race oriented
-focuses on quick throttle response
-projects at an angle for smoother bends (less friction)
-2 types for Turboed and non-turboed cars
-for gts (not gt) celicas
3. apexi gt
-race oriented
-can handle extreme horsepower (95mm piping
)
-projects at an angle for smoother bends (less friction)
-only for mr-2 and supra (no celica applications)
information taken from intensepower.com and autosportz.com where manufacturer's descriptions were summarized from