Milltek Hi-Flow Sports Cat - Audi B7 RS4 - SSXAU115

The Milltek Cat Back Hi-Flow Sports Cat for Audi B7 RS4 is a direct-fitment downpipe-mounted catalytic converter engineered to optimize exhaust scavenging and flow. T304L stainless construction with 200 CPSI high-flow catalyst element maintains emissions compliance while reducing backpressure across the rev range.

Mandrel-bent 2.5" (60mm) bore with CNC-formed catalyst housing. Hand-finished T304L stainless steel resists thermal cycling and corrosion. Designed to pair with Milltek Cat-Back systems on B7 RS4 (4.2L FSI V8). Requires Stage 2 ECU software for optimal mapping. Direct OEM hanger fitment—no modification required.

Fitment & Compatibility

• Audi B7 RS4 Sedan and Avant (2006–2008)
• Engine: 4.2L FSI V8 (BNS)
• Requires: Milltek Cat-Back Exhaust System
• Requires: Stage 2 ECU Software tuning
• Direct factory fitment—uses OEM hangers and sensor bungs

Dyno-tested for flow and thermal performance against OEM catalytic converters.

Designed and manufactured in the UK with 40+ years of performance exhaust heritage. Tested at the Nurburgring.

Specifications

• Pipe diameter: 63.5mm (2.50")
• Off-road / competition use only. Not legal for use on public roads in the US.

Fitment

• Audi > RS4 > B7 4.2 V8 Saloon, Avant and Cabriolet - V1 & ECE Systems > 2006 to 2008

• Free US shipping on orders over $250.
• Free pickup at our Dallas shop, usually ready within 24 hours.
• Unused parts can be returned within 30 days. Tunes, opened electronics, merch and installed parts are final sale.
• Want it installed? Book the install at thegbmotors.com.

Full details are on our shipping and returns page.