Stone Switchable Valve Cat Back for Mercedes E‑Class Coupe C238 M274 E250 E300 — Part No. MP518BS

Turn your C238 into the coupe it should have been from factory. This Stone valve‑controlled rear system unlocks a richer soundtrack, sharper throttle feel and true everyday usability with quiet and loud modes at the press of a button. Developed from precise 3D digitised OEM mapping for a perfect OE‑style fit, it is the ideal sound upgrade for E250 and E300 models, including 4Matic variants.

Part number: MP518BS

What makes it special

• Remote controlled valves with three modes: ON for maximum tone, OFF for discreet cruising, AUTO for RPM‑based opening via the OBD port controller
• True plug‑in setup through the OBDII socket, no splicing or complicated wiring
• Single‑piece layout with OE hanger positions and factory‑style connections for an easy, tidy install
• No motorway boom for relaxed long‑distance driving, strong character when you want it
• Multi‑axis CNC mandrel bends for consistent flow and accuracy across the system
• Robotic spot welds and overlapping joints for repeatable strength and leak‑free reliability
• Signature Stone tone: deep, refined and sporty with valves open, calm and civil with valves closed

OPF/GPF solution included

Running a particulate filter Equipped cars are supported. Stone’s OPF delete option can be supplied at no extra cost, allowing fitment on OPF/GPF vehicles without fault codes or ECU coding.

Real feedback from real installs

We have fitted this system at MJ Modifications and our customers love it. Consistently excellent fit, premium build quality and a brilliant balance of comfort and character. Quiet when you leave early, aggressive when the road opens up.

Feature highlights

• OBD valve controller with ON, OFF and AUTO modes
• 3D scanned OE geometry for precise alignment and clearance
• 7‑axis bending for smooth, consistent radius through every curve
• Clean, strong welds for durability you can trust

Compatibility

Mercedes‑Benz E‑Class Coupe C238 with M274 petrol engine:

• E250 2017+
• E300 2017+
• Includes 4Matic models

Installation

Direct replacement with OE‑style mounting points. The OBD controller simply plugs into the diagnostic port and is ready to use. For professional fitting, book with MJ Modifications in Warwickshire. Request a quote at info@mjmodifications.co.uk.

Warranty

Backed by a 2‑year Stone warranty.

Video

Search terms customers use

Mercedes E‑Class C238 sports exhaust UK, E250 performance exhaust system, E300 coupe switchable exhaust, Mercedes valve controlled exhaust with remote, active exhaust for E‑Class coupe, OBD plug‑in valve kit, quiet loud exhaust for Mercedes coupe, OPF GPF delete solution Mercedes, E‑Class 2.0 turbo sound upgrade, C238 4Matic sports back box, Mercedes E250 E300 noise adjustable exhaust, Stone UK dealer, premium exhaust upgrade for Mercedes coupe, plug and play OBD controller, drone free motorway exhaust, C238 performance cat back UK.

Part number

MP518BS