so i bought the catted FP to match w the Invidia N1 & honestly, sound difference, not to noticible but slightly louder. nothing crazy or ear busting but the noise is there. by far the EASIEST installation i have done to the car! i did struggle a little bit taking off one of the fasteners that was connected to the OP but nothing some WD40 & some elbow grease couldn't solve! no exhaust leaks & perfect fit for anyone that has an Invidia N1! highly recommend!