I've an Akrapovic evo and have used a piper cat back with a Ktec manifold they are both good but the piper has a full ktec map when fitted, the Akrapovic I fitted no mapping and was stronger down low right away no down side in a standard un mapped car. Make sure the exhaust goes all the way into the 200 funnels, so many people have fitted 200 diffusers just to melt them by not taking the extra time to make sure of this.