Expreme Exhaust Manifold Kit - 2015-2021 WRX FA20DIT

Every flaw of the OEM header has been addressed and improvised during the development of the Tomei header, resulting in power gains you can feel throughout the powerband of the car. The OEM headers restrict air flow resulting in loss of power and efficiency. Tomei headers do not restrict air flow resulting in an increase in power and efficiency.
 
The turbo side of the OEM headers severely restricts the flow of the exhaust gas, resulting in loss of power and efficiency. The collector on the Tomei headers were made using the lost wax method. The lost wax method allows the collector pipes to merge smoothly, therefore eliminating any restrictions on the header.
 
The OEM headers turbo side port is severely restricted by its 33mm port on the header. The slide adjuster on the Tomei header allows users running thicker head gaskets to appropriately extend the header to accommodate for the thicker head gasket. The flange on the Tomei headers is highly rigid, lightweight, and has a stepless flange.