Product Fitment:
2004-2021 Subaru STI
The Process West Street Billet Intake Manifold is the result of years of development, extensive testing, and multiple prototype refinements—delivering one of the most capable and proven intake upgrades available for Subaru performance applications.
Engineered for both street and high-performance builds, this manifold offers exceptional strength, precise airflow design, and consistent power gains across a wide range of setups.
Built to a Higher Standard
Every component of the manifold is CNC machined from solid billet aluminum, ensuring unmatched strength, durability, and precision compared to cast or fabricated alternatives.
Key construction highlights include:
- Precision CNC-machined billet construction
- Generous bell-mouth runner entries for improved airflow
- Thick-wall, polished mandrel-bent tubing
- High-quality TIG welding throughout
- Rated to withstand up to 100 PSI of boost pressure
This level of engineering results in a product that excels in both performance and long-term reliability.
Proven Performance Gains
Extensive testing has shown consistent improvements across all build levels:
-
~9% gains in horsepower and torque on stock setups
- Similar gains maintained on high-performance builds running E85
The carefully engineered plenum volume and runner length are optimized to deliver:
- Strong low and mid-range torque
- Smooth, consistent power delivery
- Improved top-end performance
Designed for Real-World Use
Unlike many aftermarket manifolds, the Process West Street Billet Intake Manifold is designed with practicality in mind:
- Retains factory air conditioning compatibility
- Ideal for daily-driven performance builds
- Balanced design for both drivability and power
Customizable for Advanced Builds
For more aggressive setups, additional options are available:
- Shorter billet TGVs for increased top-end power
- Custom throttle flanges available upon request
This flexibility makes the manifold suitable for everything from mild upgrades to fully built engines.
Key Features:
- CNC-machined billet aluminum construction
- Rated for up to 100 PSI boost pressure
- Optimized runner design with bell-mouth entries
- Thick-wall mandrel-bent tubing
- High-quality TIG welded assembly
- Maintains factory A/C compatibility
- Proven ~9% gains in power and torque
- Compatible with stock and modified setups
Performance Benefits:
- Increased horsepower and torque
- Improved airflow efficiency
- Strong low and mid-range response
- Sustained power through the upper RPM range
- Reliable performance under high boost conditions
