I had a custom made stainless steel centre box for my 2wd as the one you get with all the S/steel systems are too big if your car is lowered and will touch speed humps etc. It is oval shaped not round but is still pretty loud with my Scorpion rear silencer. Remember if you want to do track-days there are noise limits and with no centre box it would be way above them. I have not heard of anyone taking out the centre box completely.