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Stone Exhaust BMW B58 G20 G21 G22 G23 OEM Integrated Valved Catback Exhaust System - OPF (Inc. M340i & M440i)

Stone Exhaust BMW B58 G20 G21 G22 G23 OEM Integrated Valved Catback Exhaust System - OPF (Inc. M340i & M440i)

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We are proud to introduce you to thStone OEM Integrated Valve Catback Exhaust, to enhance the performance and sound of your BMW G20 Sedan M340i & G21 Touring M340i xDrive with the B58 engine, manufactured after 2018. Stone Exhaust has been developing world's best exhaust system since 1998, starting with 3D scanning and reverse engineering the OEM system, this allows the Stone engineers to design a 100% OEM fitment exhaust with precision. With their in-house dyno, your BMW exhaust system is proven to produce more power with the enhanced Stone signature exhaust sound.

The OEM Integred Valves option allows your exhuast system to operate as standard, where the onboard computer (ECU) will control the opening and closing of the valves automatically.


You may wish to add the Stone Valvetronic System (Singe Valve) which enables you to control the valves remotely via the stone remote controller.



  • OEM Integration
  • Available to add-on Stone Valvetronic System
  • OPF Exhaust Design
  • Plug and Play OBDII controller
  • One Piece Design
  • Mechanical Welding with Precision
  • In House Research and Development
  • 3D Scanning & Reverse Engineering
  • Dyno Developed In House
  • Eliminates drone found on the standard exhaust system


    OPF Delete

    Stone offers an OPF delete, which can be included free of charge, this allows you to install the Stone Cat-Back exhaust system on OPF equipped cars without throwing an error code, thus coding out the OPF error code on the ECU is not required.


    R&D and 3D Scanning

    Stone Exhaust engineers use reverse engineering by 3D scanning OEM parts to understand their functionality and identify weaknesses. Data has been collected continuously in order to analyze factors such as pipe diameter, route and degrees of the bending angles of the B58 Exhaust System found on the G20, G21, M340i & M340i xDrive. 

    During R&D, Stone Exhaust utilizes the 3D simulation software to stimulate the exhaust gas flow movement, thermal and pressure rise zone. Progressive improvements were continually made until the optimal performance was achieved.

    Stone Exhaust System 3D Scanning Reverse Engineering UK


    7 Axis CNC Bending Machine

    Stone Exhaust System are constructed utilizing a 7 axis CNC Bending Machine which is the ultimate machine for high levels of precision delivery, necessary for industries such as the aerospace and defense industries.

      With the state-of-the-art bending machine, Stone Exhaust has achieved the industry’s standard to an impressive 98% roundness, whilst maintaining the wear of the outer bore at only 25% at 180°. Airflow obstruction and welding fracture problems are prevented by utilizing this technology. With the combination of the CNC Bending machine, Reverse Engineering and 3D Design Scanning, Stone exhaust has created an integrally molded exhaust pipe with an accuracy error under 0.025mm.

      7 Axis CNC Bending Machine | Stone Exhaust USA


      Crisscross and Overlapping Welding Technique

      The flange between the turbo and the downpipes reaches extreme temperatures (800℃ to 1100℃) which creates stress on the connection point. By utilizing both welding techniques to increases the width and penetration of welds. This increases the endurance and tolerance of these connection points, leading to quality products with reliable performance.

      Stone Exhaust Art of Welding - Stone Exhaust USA


      Direct Spot Welding

      Our highly skilled engineers perform direct spot welding to increase product strength. This is undertaken by mechanical welding arms, proven to achieve greater precision and penetration in their welds compared to manual welding, resulting in an end product that is a work of art.

      Stone Exhaust Art of Welding - Stone Exhaust USA


      Compatibility - B58 Engine

      BMW 3 Series

      • G20 M340i/M340i xDrive (2018-2020)
      • G21 M340i xDrive (2018-2020)

      BMW 4 Series

      • G22 M440i/M440i xDrive (2020+)
      • G23 M440i xDrive (2020+)
      • G26 M440i xDrive (2020+)






      Stone Exhaust 2 Year Warranty



      Box 1: 147 cm x 31cm x 58.5cm 

      Box 2: 147 cm x 31cm x 58.5cm 



      27.36 Kg (Dual Exit with Twin Tailpipes)


      Emission Notice 

      Various U.S. states and the U.S. federal government have individual laws regulating the use of aftermarket exhaust parts and system, especially when the stock system is modified, remove, or if you are replacing original catalysts. Please consult the appropriate law department in your area before installing any aftermarket part or system on your vehicle to ensure compliance with all applicable laws. The purchasers are entirely responsible for informing themselves of the applicable laws where the products are to be used and to comply with those laws.

      If you are residing in Europe, Stone’s cat-back exhausts are OPF-compatible, which means you won’t need to code out the OPF or worry about losing your warranty.