An External Wastegate (EWG) allows exhaust gases to be diverted prior to entering the turbo. This facilitates lower backpressure at the turbine, allowing for increased boost control, faster spool-up and greater top-end power. The GrimmSpeed EWG Up Pipe has a larger internal diameter than your stock unit, allowing a higher volume of exhaust gas to reach your turbo more efficiently. This helps maintain boost levels further into your RPM range. Depending on your specific setup, these improvements can net a 10-40 HP increase. An internal wastegate can create a larger amount of turbulence in exhaust flow through your turbine housing; moving to an external wastegate eliminates much of that turbulence and isolates the turbo from what little turbulence still exists as your wastegate opens and closes. The design of each up-pipe begins with 3D scanning of the factory exhaust system, motor, subframe, firewall and downpipe. The GrimmSpeed line of 3-bolt up-pipes also involves data collection from a number of aftermarket 3-bolt headers to ensure the best possible fitment. The 3-bolt inlet flange uses a machined 45 degree transition to smoothly narrow the ID of the up-pipe to the perfect size for your stock-location turbo. The completely redesigned interlocking flex section facilitates fitment with other aftermarket components that may not be manufactured to the same exacting specifications. Additionally, the inclusion of a flex section relieves your pre-turbo exhaust system of the stresses associated with thermal expansion and contraction. Nothing says serious business like using the proper materials for the application. The flanges are machined from 1/2" thick 304 Stainless Steel plate. Tubing is CNC bent and laser cut from 14ga 304 Stainless tubing. The flex sections are made of 321 Stainless and are designed with natural frequencies that avoid those of the Subaru exhaust system. This prevents the flex section bellows from achieving resonance with the exhaust system, eliminating a massive source of fatigue. After each of these parts is manufactured and inspected, the entire assembly is TIG welded. Finally, flanges are checked for flatness before packaging. Of course, premium GrimmSpeed stainless steel gaskets are included with each pipe to ensure a perfect, leak-free seal.