4.5L Intake Manifold

The AMS Performance Subaru Intake Manifold is engineered to deliver superior performance for Subaru EJ20 and EJ25 WRX & STI models. This manifold boasts a substantial 4.5-liter plenum volume and 13-inch equal-length intake runners, meticulously designed for maximum airflow efficiency and top-end power. Constructed using a casting process, this intake manifold offers enhanced strength and allows for precise sculpting of the interior geometry to optimize power output. It features CNC-machined bellhorns that function as internal velocity stacks, contributing to a broad powerband and robust high-RPM horsepower. This intake manifold is available in both standard and reversed throttle body configurations, offering flexibility for intercooler pipe routing. It accepts larger throttle bodies up to 70mm with minor porting. The manifold is flanged for 04+ STI drive-by-wire throttle bodies, though cable throttle bodies can be adapted with custom fitting. The reversed configuration requires alternator relocation and A/C compressor removal, and both configurations may necessitate custom intercooler piping fabrication. Significant fitment considerations apply. Standard Subaru-style injectors cannot be used; aftermarket top-feed injectors with specific dimensions (48mm overall length / 11mm inlet / 14mm outlet) are recommended. It is not compatible with side-feed to top-feed conversion rails, stock rails, or top-mount intercoolers. Mounting the factory upper coolant reservoir requires custom bracketry. Additionally, due to the variety of rotated turbo kits, fitment with every brand cannot be guaranteed, and interference with the cylinder 3 intake runner is possible. Some port matching may be needed for CNC or hand-ported cylinder heads. A 2008+ STI may require minor clearancing of the A/C compressor line. This product is intended for race-only vehicles and may require a waiver for sale on emissions-controlled vehicles in the US.