Milltek M135i xDrive 5 Door F40 GPF back Exhaust SSXBM1153 Milltek Exhaust BMW 3 Series M340i G20 & G21 XDrive Saloon & Touring Milltek M135i xDrive GPF Back Exhaust System Scorpion Exhausts BMW M135i xDrive (F40 GPF Only) Gpf Back System Milltek Exhaust BMW 3 Series M340i G20 & G21 XDrive Saloon & Touring. Milltek M135i xDrive GPF Back Exhaust System SSXBM1244 Milltek has partnered with Maxton Design to bring you this beautiful exhaust system, a combination of style and performance with the Milltek x Maxton Design M135i xDrive (F40). The lightweight construction results in a weight saving of around 33% and the impressive mandrel bent design optimizes the airflow, maximizing the engines capability, and providing an excellent exhaust note that will turn heads wherever you go. (OE System Requires To Be Cut For Installation) MUST be fitted with Maxton Diffuser