Stone Exhaust Valvetronic Cat-Back Exhaust for Mercedes-Benz GLC 250 & GLC 300 (M274, X253/C253, 4MATIC/Coupe) – Remote Valves, OPF Delete – MP511S

Switchable Sports System for Mercedes GLC 250 and GLC 300 (X253 and C253) — Part MP511S

Transform your 2.0 turbo GLC with Stone’s premium valve-controlled rear section, engineered for the M274-powered GLC-Class SUV and Coupé. This remote‑operated, flap‑controlled system delivers a rich, sporty soundtrack without the cabin boom, exceptional fit straight out of the box and the day‑to‑day refinement you want for commuting and long journeys.

We run this setup on our own builds and customer cars and the feedback is consistently brilliant: crisp control over volume, quality workmanship and a truly OE‑grade installation. Part number: MP511S.

Highlights

• Valve‑controlled sound management with handheld remote: choose loud, quiet or an automatic mode that opens the flaps at a preset RPM via a plug‑in OBD port controller
• Developed using full vehicle scanning and reverse engineering for exact routing and hanger positioning
• Tight‑tolerance CNC bends, precise welding and robust joints for durability under heat and load
• One‑piece layout for strength and leak resistance
• Designed to remove the boom often associated with the factory system while unlocking a deeper tone under throttle
• OPF/GPF support included: supplied with a solution for particulate filter‑equipped cars, avoiding warning lights and without ECU coding

Everyday calm, press‑button aggression

With the valves shut, cruising is civil and comfortable. Open them and the M274 turbo four comes alive with a clean, aggressive note and freer flow. AUTO mode uses the OBD plug‑and‑play module to open at your chosen engine speed, giving you intelligent noise control without fuss.

Engineered properly

Stone’s process starts with 3D scanning of the OEM system, followed by digital flow simulation to optimise diameter, routing and bend geometry. The result is a precision fit, consistent quality and a performance‑focused sound profile. Expect accurate bends, high‑penetration welds at hot spots and repeatable, factory‑like alignment.

Vehicle compatibility

For Mercedes models with the M274 petrol engine:

• X253 GLC 250 4MATIC (2015+)
• X253 GLC 300 and GLC 300 4MATIC (2015+)
• C253 GLC 250 Coupé 4MATIC (2015+)
• C253 GLC 300 Coupé and GLC 300 Coupé 4MATIC (2015+)

Why buy from us

MJ Modifications has fitted and tested this Stone system on multiple GLC builds. Our customers love the refined cruising and the switchable roar on demand, plus the neat factory‑level fitment and hassle‑free valve control.

Professional installation

Prefer expert fitting? Book your install with MJ Modifications in Warwickshire. Email info@mjmodifications.co.uk for a quotation and availability.

Part number

MP511S

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