i think the main difference why the G35 has a difference sound than the TSX is because of the engine..TOTALLY different engines will create TOTALLY different sounds..
the G coupe is a 3.5 litre V6 where as the TSX is only a 2.4 litre inline-4
i dont know if the G coupe exhaust will fit..but EVEN IF IT DOES..the sound created will not be the same..
if you want a nice sound from the exhaust, try looking into aftermarket exhaust solutions like fujitsubo..there are a couple sound clips posted recently