i think a true dual with 2 1/2 inch will be plenty . i would get a couple a mandrel bent pieces for the sharp turns on the drivers side. free flow cats work great but remember that the factory cats work good as well. i run carsound cats on mine. they work good. i am also running a magnaflow hd muffler. 12568 it the poart number. it has a dual inlet and outlet. it also has a true x pipe design inside that will help low end some.