MBRP 15.5-16 GM Duramax 6.6L 3in Down Pipe KitMBRP 15. 5 16 GM Duramax 6. 6L 3in Down Pipe Kit Replace that restrictive factory downpipe with a MBRP direct replacement downpipe for more flow, fuel economy, and better performance. Removal of OEM catalytic converters may be a violation of emissions laws in your jurisdiction. Ensure that the intended use of this product is permitted. Not for sale or use in the state of California. Armor BLK Turbocharger Down Pipe; 3 in.; Black Coated; For Use w 3