Exhaust Retro Kit for Chevrolet Silverado GMC Sierra (2007-2013) 4.8L 5.3L 6.0L EnginesMandrel Bent Dual Exhaust Retro Kit for 2007 2013 Silverado, Sierra (Vortec GMT900) This retro kit converts the restrictive factory single exit exhaust into a high flow dual rear exit system to reduce backpressure and improve exhaust scavenging for GMT900 platform trucks. Fabrication maybe required. Not Plug and Play. The Stock Silverado, Sierra Exhaust Bottleneck The OEM exhaust on 2007 2013 Silverado and Sierra models utilizes a high volume, single