hmf exhaust & rear faring


i would like to know if i put a hmf exhaust sys on will i need to get a pc2 or will a tre be enough?also if i install the top gun will it be required to cut the rear faring?
i put the topgun undertail on myself, all you have to cut off is the black plastic mudflap in the back and on the sides. The new undertail fits on with the original pushpins and it fits perfectly without any ugly gaps. The undertail also covers up everything that gets cut off so it doesn't matter if its cut perfectly staight or not.