The part number is engraved on the front end of oval silencer at the top if standard system or on a stainless plate tack welded to top side of silencer inlet pipe if an optional sports system Adam. You can check with a mirror or phone camera in-situ. If it's an optional factory sports system it will have an AER prefix indicating it's an Aero Racing part. Both side and rear exit sports systems were offered for Plus 4 and Roadsters and have round silencer box.
