Over the years, GrimmSpeed has proven that our exhaust products are some of the highest-quality and best-performing in the industry because of the detail oriented approached that we put into their development. When it comes to improving on an OEM design, this attention to detail and overall exhaust knowledge allows us to identify aspects of the factory parts that can be greatly improved upon. One of the first things to note about the OE exhaust manifold are the several points where flow is decreased due to a neckdown in piping diameter. These disruptions in exhaust flow result in decreased turbine efficiency which ultimately limits boost and power production. Furthermore, the OE merge collectors are made specifically with ease of manufacturing in mind and the result is a compromise on performance. The collectors contain very odd shapes that are bad for smooth exhaust flow and have several diameter restrictions that make them one of the biggest weaknesses of the stock manifold. Finally, the angle of the exhaust flow merge is also not ideal, causing the exhaust pulses to “fight” each other, which can add to flow differences for the twin scroll turbine, sacrificing spool and performance.