The most common points of failure on the Ford 6.0L Powerstroke Y-Pipe are the corrugated bellows which become heat-fatigued and crack over time causing power robbing pre-turbo exhaust leaks over time. Replacing the stock flex joints can cost you considerable time and money for a repair that will only fail again in time. But, deleting them altogether in favor of straight tubing can cause serious long term damage from heat expansion and vibration that can cause stress fractures and more exhaust leaks. On the Sinister Diesel Y-Pipes for the 6.0L Powerstroke, we have opted to get rid of the factory bellows-style joints in favor of a much stronger and longer-lasting flex joint. The new design still allows the upper and lower sections of the Y-Pipes to move due to heat expansion while maintaining a complete seal.