Stone Exhaust Mercedes GLA 45 AMG GLA45 (X156, M133 2.0T) Valved/Active Cat-Back Catback Performance Exhaust System - Switchable Flap, Remote OBD-II/OBD2 Plug & Play - Drone-Free, OEM Direct Fit - OPF/GPF Compatible Sports Exhaust Upgrade UK

Stone Exhaust for Mercedes GLA 45 AMG X156 M133 Cat Back with Switchable Valves

Give your Merc GLA 45 AMG the soundtrack and response it deserves. This Stone Exhaust rear system is built for the X156 chassis with the M133 turbo engine, delivering a deeper, richer tone under load with refined manners on the motorway. The result is a performance exhaust that sounds premium, avoids annoying cabin resonance, and lets you choose quiet or loud at the touch of a button.

Stone have been crafting high-performance systems since 1998. Every assembly is digitally scanned from factory components, reverse engineered for a direct bolt-on install, then refined on the dyno to balance flow, tone, and drivability. The outcome is a GLA 45 upgrade that fits perfectly, looks superb and performs consistently.

Highlights

• Designed specifically for the Mercedes GLA 45 AMG X156 with the M133 engine code
• Cat back layout with valve-controlled sound for street comfort and track-ready character
• Wireless controller with ON, OFF and AUTO modes for instant soundtrack changes
• OBD port plug-in module for a clean, fast install with no cutting of factory wiring
• No droning in the cabin compared to many aftermarket systems
• Exact-fit geometry based on 3D scans of OEM parts for hassle-free mounting
• Dyno-developed for balanced performance and a crisp AMG tone

Switchable valves. Quiet when you need it, fierce when you want it

Use the supplied remote to open or close the valves on demand, or choose AUTO so the valves open at a set RPM point. Daily drive in peace, then unleash the growl when the road opens up. The plug-in controller uses the vehicle’s OBD port for a tidy, reversible installation.

Built for precision and longevity

• 7-axis CNC mandrel bending maintains perfect roundness and smooth flow paths
• Overlapped and crisscross welds reinforce high-heat joints for durability
• Robotic spot welding improves penetration and consistency across every seam
• Integrally formed sections minimise turbulence for efficient gas velocity
• Single-piece sections where possible for strength and leak resistance

OPF/GPF compatibility

Running a particulate filter on your GLA 45 AMG X156? An OPF/GPF solution is available on request at no extra cost. This enables installation without warning lights, avoiding the need to code out the filter on the ECU.

Fitment and installation

Application: Mercedes-Benz GLA 45 AMG X156 with the M133 engine.

Professional fitting available at MJ Modifications in Warwickshire. For a tailored installation quote, email info@mjmodifications.co.uk.

Part number

MO504NS

Manufacturer and warranty

Manufactured by Stone Exhaust and supplied with a 2 year warranty.

What our team thinks

We have installed this switchable-valve cat back on multiple AMG platforms. The fit is spot on, the finish is excellent, and customers love the ability to cruise quietly then open the valves for that clean, aggressive AMG note. It is a go-to upgrade for GLA 45 owners who want a premium sound without cabin boom.

Video

Stone Valve-Controlled System Installation

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