PROFILEARM Motorsports' N63R downpipes for the 4.4L V8 Twin-Turbo powered M550i allows you to take your N63R engine to the next level. Made with full 304 Stainless Steel and 3" construction these downpipes open up an incredible sound from the twin turbocharged V8 even with the stock exhaust!By replacing the OEM downpipes with the ARM N63R Catless Downpipes, you'll be removing the restriction from the OEM converters which will reduce exhaust back-pressure and allow the exhaust from the turbochargers to flow more freely. This increase in exhaust flow allows for the turbos to spool faster, increasing power and torque throughout the RPM range of your M550i. N63R DOWNPIPE DESIGNAs with all BMW's, everything is designed to fit in a very compact space, and the N63R M550i downpipes are no exception. However, BMW did an excellent job of engineering the downpipes to flow in the smoothest path from the turbocharges down to the mid pipe section. Our downpipes essentially followed the same exhaust flow path with a few small modifications to make airflow smoother and installation easier. Consequently, the ARM N63R downpipes mount up to the turbos and midpipes with the same precision as you would expect from the factory M550i downpipes. The ARM N63R M550i downpipes come with a mesh flex section to relieve stress between the upper and lower portion of the downpipe. To further reduce any tension on the turbochargers, we have developed an upper and lower bracket, one welded on the section of pipe above the flex joint where it secures to the engine block, and the other on the lower portion below the flex joint where it is secured to the transmission housing. These are the same points BMW designed their factory M550i downpipes to be secured, which means a strong and lasting connection safe for all of the components on the vehicle.The ARM N63R M550i downpipes utilize two O2 sensor bungs on each downpipe to allow for reinstalling the O2 sensors in their factory locations. This allows the correct oxygen sensor data to be sent to the DME. This is essential for the DME to properly monitor the fuel mixture in the exhaust gas that are critical to having your M550i motor running smoothly.