Milltek Sport HJS Tuning 300-Cell ECE Approved Downpipe/Sports Cat for BMW 3 Series F30/F31 LCI 340i/M340i Saloon & Touring (xDrive & RWD) 2017-2020 - T304 Stainless - SSXBM1039_2

BMW 340i/M340i F30/F31 LCI Sports Catalyst Front Pipe with HJS 300cpsi Core — Part No. SSXBM1039_2

Unlock your B58’s potential with this high-flow, ECE-approved HJS metal core sports catalyst front section. Crafted in the UK from premium 304-grade non-magnetic stainless steel, this performance-focused front pipe delivers freer exhaust flow, quick spool and a richer, sharper soundtrack while retaining everyday refinement. It is a superb quality upgrade for drivers who want real-world gains, exceptional build quality and road-friendly compliance in applicable regions.

We run this hardware on customer cars and our own builds and the feedback has been consistently excellent: precise fitment, robust welds, clean OEM-style integration and a sound that adds character without unwanted cabin boom. If you are hunting for a high-flow cat for your BMW 340i or M340i that balances performance with sophistication, this is the go-to choice.

Key reasons enthusiasts choose this setup

• HJS 300 cpsi Euro-approved metal catalyst for high throughput and road-going compliance where applicable.
• 304 stainless construction for corrosion resistance, heat durability and a finish that resists discolouration.
• Mandrel-formed bends maintain a constant internal diameter for smooth gas velocity and reduced back pressure.
• Optimised bore for improved response without sacrificing mid-range drivability.
• Tuned acoustics: deeper tone under load, refined cruise with no intrusive cabin drone.
• UK-built to tight tolerances for an accurate, hassle-free install.

Compatibility

• BMW 3 Series F30 LCI 340i/M340i Saloon 2017–2020 — xDrive and rear-wheel drive
• BMW 3 Series F31 LCI 340i/M340i Touring 2017–2020 — xDrive and rear-wheel drive

Tech details

• Part number: SSXBM1039_2
• Catalyst: HJS 300 cell metal substrate, ECE approved
• Material: T304 stainless steel, non-magnetic
• Application: BMW B58-powered 340i/M340i F30/F31 LCI 2017–2020

What you can expect on the road

• Smoother exhaust flow that complements software tuning and hardware mods.
• Crisp, more engaging turbo note on throttle, with a calm motorway cruise.
• Quality you can see and feel, engineered for long-term use in the UK climate.

Installation and support

Professional fitting recommended. Book your installation with MJ Modifications in Warwickshire — request a quote at info@mjmodifications.co.uk.

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