HELP NEEDED. IVE GOT A 98 IMPREZA SPORT WITH A STANDARD EXHAUST. I WANT TO FIT A BACK BOX FROM A 94 WRX BUT THE FLANGE ON THE TURBO BOX IS SLIGHTLY BIGGER. DO I HAVE TO CHANGE THE WHOLE THING OR CAN I JUST CHANGE THE CENTRE SECTION .? ANY HELP WOULD BE GOOOD