Exhaust› Exhaust Pipes, Systems and Components

Milltek

Sport Cat-Back Exhaust System with Quad GT-90 Tips

$3,756.77

SKU: SSXAU644

Special Order
Special Order
Ships in 4–6 weeks
Free Shipping over $200
$100 Minimum Order
30 Days Return
INSTALL DIFFICULTY
DIY PRO SHOP

Moderate — 2–4 hours

Overview

The Milltek SSXAU644 is a resonated cat-back exhaust system designed as a direct replacement for the original system. It is constructed from 2.50" T304 anti-magnetic stainless steel, ensuring durability and resistance to discoloration. This system features Quad GT-90 90mm polished tips and retains the factory exhaust valve operation.
Show original supplier description
The Milltek SSXAU644 is a resonated cat-back exhaust system engineered to enhance the sound and aesthetics of your vehicle while maintaining a responsible noise level. Designed as a direct replacement for the factory exhaust, this system requires no modifications for proper fitment and utilizes OEM hangers. Constructed from 2.50" T304 anti-magnetic stainless steel, the SSXAU644 is built for longevity and resistance to harsh conditions and discoloration. The pipework, mufflers, and resonators are all made from this premium material. Mandrel bending ensures smooth, full-flow bends for improved exhaust gas flow, and an increased bore diameter contributes to optimal performance without sacrificing mid-range torque. This cat-back system allows you to retain the use of your vehicle's factory exhaust valve system. The valved mufflers seamlessly integrate with the car's vacuum system, reusing the OE valves and operating as stock through the Drive Select options. The kit includes two post-cat downpipes, a center front silencer section, two valved rear mufflers, Quad GT-90 90mm polished tips, and all necessary installation hardware. This exhaust system is specifically designed for Audi B9 S4 and S5 models with the 3.0T Quattro engine, excluding models with a factory rear sports differential. It is covered by a limited lifetime warranty for anti-corrosion and manufacturer defects.

Product descriptions are provided by our supplier partners and may not always be perfectly accurate. Not sure this fits? or call (760) 282-4645 and we’ll verify before you order.

Fitment

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Specifications

BrandMilltek
Part NumberSSXAU644
CategoryExhaust
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Returns & Fitment

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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Shipping

Orders are processed in 1–3 business days. In stock parts ship promptly from our partner network. Special-order items either aren’t currently stocked or are built to your spec — expect 4–6 weeks. If a part goes on backorder while your order is in the queue, we’ll reach out and work through discounted alternatives together.

Free shipping over $200 in the continental US. Alaska, Hawaii, U.S. territories (Puerto Rico, U.S. Virgin Islands, Guam, American Samoa, and the Northern Mariana Islands), and international orders carry surcharges — most appear at checkout. Some exceptions (LTL freight, or suppliers who quote freight only after we place the order) won’t. In those cases we’ll reach out with the exact charge before your order moves forward.

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