Milltek Sport OPF/GPF Bypass Delete For BMW G80 M3 / G82 M4GPF OPF Delete bypass pipe by milltek, Please choose from the drop down menu if you want Resonated or Non Resonated (louder). Also choose if you would like OE Fitment (to fit onto original catback) or Milltek fitment (to fit onto milltek cat back) Please note A stage 2 map will be required or an opf bypass module found here This will stop the vehicle EML light coming on. 76mm 3" Pipe Diameter