Turbo XS 08-21 Subaru WRX STi Boost Control Solenoid Kit - WS08-BCS

The Turbo XS Boost Control Solenoid Kit (WS08-BCS) is a direct-fit upgrade engineered specifically for the 2008–2021 Subaru WRX STI, replacing the factory 2-port boost solenoid with a superior 3-port unit. If you've installed an aftermarket downpipe or an upgraded turbocharger on your STI, this solenoid kit is a required companion piece — without it, precise boost control simply isn't possible. It's a purpose-built solution for serious STI owners who demand consistent, controllable boost delivery to match their performance modifications.

Key Features & Benefits

• 3-Port Design Replaces the Factory 2-Port Solenoid: The stock 2-port boost control solenoid is a limiting factor once you start modifying your STI's turbo system. The Turbo XS 3-port solenoid provides an additional control port, giving your engine management system greater authority over boost pressure — a prerequisite for dialing in a proper tune on a modified car.
• Required for Aftermarket Downpipe & Upgraded Turbo Builds: This is not a purely optional upgrade. When running an aftermarket downpipe or a larger turbocharger on your 2008–2021 STI, the factory solenoid cannot keep up with the demands of a proper tune. The WS08-BCS resolves that limitation directly.
• Direct-Fit Application: Designed specifically for the 2008–2021 Subaru WRX STI platform, so you're not adapting a universal part — fitment is deliberate and vehicle-specific.
• Turbo XS Engineering Pedigree: Turbo XS is a well-known name in the Subaru performance community, with a catalog spanning blow-off valves, intercoolers, exhausts, and boost management components across multiple WRX and STI generations.
• Supports Accurate Boost Tuning: Upgrading to a 3-port solenoid is a foundational step for anyone working with an aftermarket ECU tune, as it gives the tuner a more responsive and capable tool for managing boost curves across the RPM range.

Specifications

• Brand: Turbo XS
• Part Number (MPN): WS08-BCS
• SKU: TXSWS08-BCS
• UPC: 053176488561
• Port Configuration: 3-port (replaces OEM 2-port)
• CARB Compliance: Not CARB legal; not for sale in California
• Proposition 65: Yes — California Proposition 65 warning applies

Fitment

The Turbo XS WS08-BCS Boost Control Solenoid Kit is confirmed to fit the following Subaru WRX STI applications:

• 2008–2014 Subaru Impreza WRX STI
• 2015–2021 Subaru WRX STI — Base
• 2015 Subaru WRX STI — Launch Edition
• 2015–2021 Subaru WRX STI — Limited
• 2016–2017 Subaru WRX STI — Series.HyperBlue
• 2018–2019 Subaru WRX STI — Type RA
• 2019 Subaru WRX STI — S209

Important note: This kit is designed for the WRX STI across these model years. If you own a standard WRX (non-STI) from 2008–2014, confirm fitment with our team before ordering, as the STI and WRX use different turbo systems. This product is not for sale in California as it is not CARB compliant.

Why Buy from ThreePiece.us

• Free Shipping on Every Order: The Turbo XS WS08-BCS ships free to your door — no minimum order required.
• Affirm Financing Available: Break your purchase into manageable payments with Affirm. Building out your STI's boost system doesn't have to hit your wallet all at once.
• Expert Fitment Support: Not sure if the WS08-BCS is the right piece for your specific build or tune setup? Our team has served 10,000+ customers and can help you verify fitment and compatibility. Reach us at 813-535-5801 or via email at [email protected].
• In-Stock Availability: This item is a regularly stocked product — no lengthy waits on this performance essential.

Frequently Asked Questions

Q: Why do I need a 3-port boost control solenoid for my STI?
A: The factory STI boost control solenoid is a 2-port unit. When you add an aftermarket downpipe or upgrade to a larger turbocharger, the stock solenoid becomes a bottleneck for accurate boost management. The Turbo XS WS08-BCS replaces it with a 3-port solenoid, which is required for proper boost control in a modified STI application.

Q: Does this solenoid fit the standard WRX (non-STI)?
A: The WS08-BCS is specifically listed for the WRX STI from 2008–2021. The standard WRX and the STI use different turbo systems. If you drive a non-STI WRX, contact our fitment team at 813-535-5801 before ordering so we can confirm compatibility for your exact vehicle.

Q: Is this product legal to use in California?
A: No. The Turbo XS WS08-BCS is not CARB (California Air Resources Board) legal and cannot be sold to California residents. It is intended for use in off-road or racing applications, or in states that do not require CARB compliance.

Q: How long will it take to receive this part?
A: The WS08-BCS is a regularly stocked product at ThreePiece.us — it is not a special-order item. Orders ship free, and you can reach our team at 813-535-5801 if you have questions about your specific order timeline.