OP, if you don't want it to drone, you may have to keep it to 2 1/2. In sections. J pipes are the way to go. So add a dual straight through muffler in exchange for the factory. and no rear mufflers, use j pipes for this section. Another exhaust shop in Adelaide who are on the expensive side, but the work speaks for itself is aaa exhaust Richmond. Mark from exhaust tech, kpm, are all good! The work is good! But I personally won't use them because there always a good $300 to $400 more then anyone else. There's this old saying you get what you pay for and in this case it's true! Also check out member pir4te exhaust. Henholtz chambers I think there called! They work! I've got headers, 100cpi cats, 3 inch, h pipe, into 2 1/2 dual muffler back into 3 inch j pipes. Quiet at idle, no drone and deep loud rumble when I flatten it.