{"product_id":"stone-exhaust-bmw-n55-f25-f26-cat-back-valvetronic-exhaustinc-x3-35i-xdrive-x4-35i-xdrive-x4-m40i-xdrive","title":"Stone Exhaust Valvetronic Cat-Back for BMW N55 F25\/F26 — X3 35i xDrive, X4 35i xDrive, X4 M40i xDrive | Valved Performance Exhaust | Plug \u0026 Play OBDII Controller | AP531S\/AP531BSQ","description":"\u003cdiv class=\"product__description rte\"\u003e\n  \u003ch2\u003eSwitchable Cat Back System for BMW F25 F26 N55 - X3 35i xDrive, X4 35i xDrive, X4 M40i xDrive\u003c\/h2\u003e\n\n  \u003cp\u003e\n    Unlock the soundtrack and response your turbocharged straight six deserves. This Stone valve-controlled cat back transforms the F25 and F26 platform with a deep performance tone under load and calm, refined manners on the motorway. Developed using 3D scanning, reverse engineering and in-house dyno validation, it delivers OEM-style fitment, smooth flow paths and the flexibility of quiet or loud at the touch of a button.\n  \u003c\/p\u003e\n\n  \u003cp\u003e\n    Ideal for drivers searching for a switchable sports exhaust for BMW X3 35i or X4 35i, a flap-controlled system for the X4 M40i, or a plug in OBD port controller solution for the N55B30 engine. If you are comparing rear section upgrades, muffler replacements, performance systems for the X3 petrol turbo or X4 petrol turbo, this is the premium option that balances civility with genuine performance character.\n  \u003c\/p\u003e\n\n  \u003ch3\u003eVehicle compatibility\u003c\/h3\u003e\n  \u003cul\u003e\n    \u003cli\u003eBMW X3 F25 35i xDrive - N55\u003c\/li\u003e\n    \u003cli\u003eBMW X4 F26 35i xDrive - N55\u003c\/li\u003e\n    \u003cli\u003eBMW X4 F26 M40i xDrive - N55\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003ch3\u003eWhat makes it stand out\u003c\/h3\u003e\n  \u003cul\u003e\n    \u003cli\u003eSwitchable valves with remote control - choose quiet, loud or automatic operation\u003c\/li\u003e\n    \u003cli\u003eComfortable, low-drone cruising with a rich, aggressive tone under throttle\u003c\/li\u003e\n    \u003cli\u003eOBD port plug in module - no cutting, no splicing, simple installation\u003c\/li\u003e\n    \u003cli\u003eAutomatic mode can be set to open at your chosen RPM for the best of both worlds\u003c\/li\u003e\n    \u003cli\u003e3D-scanned and reverse-engineered for true OEM-like fit and alignment\u003c\/li\u003e\n    \u003cli\u003eDyno-developed to sharpen response and optimise flow on the N55 platform\u003c\/li\u003e\n    \u003cli\u003ePrecision mechanical welding with long, smooth bends for consistency\u003c\/li\u003e\n    \u003cli\u003e7-axis CNC-bent sections promote roundness and reduce turbulence\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003ch3\u003eValve control - sound on your terms\u003c\/h3\u003e\n  \u003cul\u003e\n    \u003cli\u003eON - valves open for maximum flow and an authentic straight six soundtrack\u003c\/li\u003e\n    \u003cli\u003eOFF - valves closed for neighbour-friendly cold starts and long journeys\u003c\/li\u003e\n    \u003cli\u003eAUTO - user-defined RPM trigger opens the valves when you want the noise\u003c\/li\u003e\n    \u003cli\u003eTrue plug in OBDII controller - quick to install and easy to live with\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003ch3\u003eEngineering detail that matters\u003c\/h3\u003e\n  \u003cul\u003e\n    \u003cli\u003eCAD-led development for perfect F25 and F26 chassis integration\u003c\/li\u003e\n    \u003cli\u003eFlow path simulation guides pipe routing and diameters for smooth gas speed\u003c\/li\u003e\n    \u003cli\u003eCNC bending keeps the tube profile round for cleaner, faster flow\u003c\/li\u003e\n    \u003cli\u003eAdvanced weld techniques provide strength and durability at high temperature\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003ch3\u003eTailpipe options and part numbers\u003c\/h3\u003e\n  \u003cul\u003e\n    \u003cli\u003e\n\u003cstrong\u003eAP531S\u003c\/strong\u003e - Dual exit with twin tailpipes - requires M40i rear valance\u003c\/li\u003e\n    \u003cli\u003e\n\u003cstrong\u003eAP531BSQ\u003c\/strong\u003e - Dual exit with quad tailpipes - requires M40i rear valance\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003ch3\u003eInstallation\u003c\/h3\u003e\n  \u003cul\u003e\n    \u003cli\u003eDirect bolt-on using OEM-style hangers and mounts for F25 X3 and F26 X4\u003c\/li\u003e\n    \u003cli\u003eOBDII controller installs in minutes\u003c\/li\u003e\n    \u003cli\u003eProfessional fitting recommended to ensure perfect tip alignment and clearance\u003c\/li\u003e\n  \u003c\/ul\u003e\n  \u003cp\u003e\n    Prefer a hassle-free install by specialists who know these cars inside out? Book fitting with MJ Modifications in Warwickshire. Request a quote: \n    \u003ca href=\"mailto:info@mjmodifications.co.uk\"\u003einfo@mjmodifications.co.uk\u003c\/a\u003e.\n  \u003c\/p\u003e\n\n  \u003ch3\u003eTried and loved by our customers\u003c\/h3\u003e\n  \u003cp\u003e\n    We have supplied and fitted these Stone systems on X3 and X4 N55 models and feedback has been consistently brilliant. Owners praise the premium sound quality, the calm cruising with valves shut and the instant drama at the press of a button. If you are searching for a switchable sports exhaust for BMW X3 35i, X4 35i or X4 M40i in the UK, this is the upgrade we recommend.\n  \u003c\/p\u003e\n\n  \u003ch3\u003eWarranty\u003c\/h3\u003e\n  \u003cp\u003eStone Exhaust 2 year warranty.\u003c\/p\u003e\n\n  \u003ch3\u003eBrand\u003c\/h3\u003e\n  \u003cp\u003eStone Exhaust\u003c\/p\u003e\n\n  \u003ch3\u003eWatch and listen\u003c\/h3\u003e\n  \u003cp\u003eStone Valvetronic System Installation\u003c\/p\u003e\n  \u003cdiv class=\"video-wrapper\" style=\"position:relative;padding-bottom:56.25%;height:0;overflow:hidden;\"\u003e\n    \u003ciframe src=\"https:\/\/www.youtube.com\/embed\/V5c4VEyO1EM\" title=\"Stone Valvetronic System Installation\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen style=\"position:absolute;top:0;left:0;width:100%;height:100%;\"\u003e\u003c\/iframe\u003e\n  \u003c\/div\u003e\n  \u003cp\u003eBMW X4 35i catless downpipe sound with Stone system\u003c\/p\u003e\n  \u003cdiv class=\"video-wrapper\" style=\"position:relative;padding-bottom:56.25%;height:0;overflow:hidden;\"\u003e\n    \u003ciframe src=\"https:\/\/www.youtube.com\/embed\/cmVUX0EnEFM\" title=\"BMW X4 35i Catless Downpipe Sound\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen style=\"position:absolute;top:0;left:0;width:100%;height:100%;\"\u003e\u003c\/iframe\u003e\n  \u003c\/div\u003e\n\n  \u003ch3\u003eSearch phrases people use\u003c\/h3\u003e\n  \u003cp\u003e\n    BMW X3 F25 35i sports exhaust UK, BMW X4 F26 35i sports exhaust UK, X4 M40i switchable exhaust, valve controlled exhaust for N55, flap control exhaust for BMW, OBD plug in exhaust controller, remote controlled exhaust flaps, cat back system for BMW X3 petrol turbo, cat back system for BMW X4 petrol turbo, rear silencer upgrade BMW N55, performance exhaust for X3 3.0 turbo, performance exhaust for X4 3.0 turbo, quad exit exhaust for X4, twin exit exhaust for X3, BMW F25 exhaust upgrade UK, BMW F26 exhaust upgrade UK, best sounding exhaust for N55, UK installer Warwickshire BMW exhaust, AP531S, AP531BSQ.\n  \u003c\/p\u003e\n\u003c\/div\u003e","brand":"Stone Exhaust","offers":[{"title":"Dual Exit with Twin Tailpipes \/ Require M40i bumper \/ Flat Cut Gloss Carbon Fiber (82mm)","offer_id":55978667671938,"sku":null,"price":3056.64,"currency_code":"GBP","in_stock":true},{"title":"Dual Exit with Quad Tailpipes \/ Require M40i bumper \/ Flat Cut Gloss Carbon Fiber (82mm)","offer_id":55978667704706,"sku":null,"price":3150.72,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0871\/5445\/8937\/files\/1020CG_FlatCutGlossCarbonFibre_102mm-2_1024x1024_2x_36052d95-81f2-49a6-9e42-a7a4fe3304c9.webp?v=1763380154","url":"https:\/\/mjmodifications.co.uk\/products\/stone-exhaust-bmw-n55-f25-f26-cat-back-valvetronic-exhaustinc-x3-35i-xdrive-x4-35i-xdrive-x4-m40i-xdrive","provider":"MJ Modifications","version":"1.0","type":"link"}