Process West Dual Fuel Rail Billet Tumbler Delete Kit - Subaru 01-07 WRX/STI & 08-21 STI - Black

This bolt-on upgrade addresses the two biggest bottlenecks in the EJ-series intake system: air restriction and fuel supply.

CNC machined from billet aluminium, the kit replaces the restrictive factory assembly with precision-machined billet components, for maximum airflow and reliable fuel delivery in high-boost applications.

Billet Tumbler Delete

The factory Tumble Generator Valves (TGV, often called tumblers) use butterfly valves in the intake runners. These create severe restriction, especially at mid to high rpm. The billet tumbler delete removes this bottleneck:

• Unrestricted flow: CNC machined from billet aluminium with a high-flow, smooth internal runner.
• Power gains: Smoothing the path of air into the cylinder heads removes a major choke point, for measurable increases in horsepower and torque across the rev range.
• Precision design: Smooth, radiused inlet and outlet profile for maximum laminar flow into the cylinder head ports.

Dual Fuel Rails

On builds with upgraded turbos, injectors and E85 or race fuels, the factory single-feed fuel system is inadequate. The integrated dual fuel rails address fuelling inconsistencies under high load:

• Consistent fuel pressure: The dual-rail design supports larger injectors and provides a reliable, uninterrupted flow of fuel, preventing the fuel starvation common in highly tuned applications.
• High-volume ready: Important for high-horsepower builds, so the engine receives the required volume of fuel when running increased boost or alternative fuels such as E85.
• Integrated design: Built into the TGV delete assembly, reducing complexity and potential failure points compared with separate rail and spacer kits.