With the nos you would still want to increase flow with exhaust and intake, port the headder then 2.5" from the cat makes a difference. Cat could be removed if you wanted but the factory cat is ok. The factory pipe out of the cat is not the best and chopping into the cat is better. An Injen or TRD intake would work well. Use a long 2 x 14" or 18" resonator with rear magnaflow etc This power would be fine as long as you have the extra fuel the fuel system may need an upgrade. The current systems pump may need an upgrade and a return fuel line.