Let's start with my objective: increase the torque and achieve at lower rpm; maintain the max power or (better) increase it.
Wich exhaust diameter should I choose? 2,5in or 3in?

It seems that larger exhaust diameter increase the power but the max torque is achieved at higher rpm...

I would appreciate a dyno chart with before and after a cat back system with torque curve from 1500rpm to 7500rpm.

I'm between Ralliart 2,5 vs Fujitsubo 3.

Someone could help me?