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Description
APR Catback Exhaust System - Audi / B9 / S4 / S5Introducing the APR Catback Exhaust System for the Audi B9 S4 and S5 The APR Catback Exhaust System for the Audi B9 S4 and S5 is a complete, high performance exhaust solution that runs the entire length of the vehicle from the catalyst back. Inspired by the larger center pipe design of the higher output RS4 and RS5 models, this system is engineered to boost performance, elevate sound, and enhance aesthetics with customizable exhaust tips that are sure
Introducing the APR Catback Exhaust System for the Audi B9 S4 and S5
The APR Catback Exhaust System for the Audi B9 S4 and S5 is a complete, high-performance exhaust solution that runs the entire length of the vehicle from the catalyst back. Inspired by the larger center-pipe design of the higher-output RS4 and RS5 models, this system is engineered to boost performance, elevate sound, and enhance aesthetics with customizable exhaust tips that are sure to make a statement. Crafted from premium materials and built with advanced manufacturing techniques, this system is designed to withstand harsh conditions and deliver lasting performance. Expect a bold, aggressive growl at wide-open throttle, along with an impressive gain of 10 horsepower and 12 FT-LBS of torque to all four wheels!
Unmatched Design and Precision Engineering
Unlike anything currently available, the APR system includes downpipes extending to the factory catalyst in the upper engine bay, making this a true full-system upgrade. We’ve minimized restrictions with smooth transitions, oversized piping, and straight-through mufflers and resonators. Constructed from mandrel-bent T304 stainless steel with a brushed finish and TIG welding throughout, this exhaust system is as durable as it is striking. Installation is hassle-free, thanks to precision-fit brackets, OEM-style slip clamps, and an included upgraded tunnel brace to accommodate the oversized piping.
Inspired by RS Performance
Like the RS4 and RS5, this system features a reengineered exhaust routing design. It utilizes dual 2.5” (63.5mm) downpipes to dual 2.75” (70mm) midpipes pipes merging through a cast Y-junction into a massive 3.5” (91mm) midpipe, replacing the restrictive factory dual-pipe setup. The integrated Helmholtz resonator minimizes drone through a straight-through design with a sound-canceling port, ensuring no compromise in exhaust flow.
The system splits again via another cast Y into two rear, valve-controlled mufflers with sound absorption technology. These valves are fully integrated with the OEM control system, adjusting automatically to enhance sound during aggressive driving while maintaining a quieter profile during cruising. Finally, exhaust gases exit through dual cast Y-junctions into a quad 2.5” (63.5mm) system, terminating in 3.5” (91mm) lightweight, single-walled motorsport-style tips. The tips feature a polished stainless steel finish and a subtle APR logo for a refined touch.
Experience the APR Difference
Designed for enthusiasts seeking the perfect balance of power, sound, style, and quality, the APR Catback Exhaust System for the Audi B9 S4 and S5 is a testament to engineering excellence. With its performance-driven design and durable construction, this system not only transforms your driving experience but also ensures years of reliable performance.
Features:
- Complete catalyst-back system including downpipes, extending from the factory catalyst back.
- Performance gains of 10 HP and 12 FT-LBS of torque delivered to all four wheels.
- Premium T304 stainless steel construction with TIG welding for strength and durability.
- Optimized flow through dual 2.5” downpipes, 2.75” midpipes, and a 3.5” midpipe.
- Mandrel-bent brushed piping paired with electropolished cast splitters for a refined finish.
- Precision brackets and slip clamps ensure accurate alignment and hassle-free installation.
- Includes an upgraded tunnel brace to accommodate the larger piping.
- Integrated Helmholtz resonator minimizes drone and enhances sound quality.
- Valve-controlled rear mufflers dynamically adjust sound based on driving style.
- Removable quad 3.5” motorsport-style polished tips with APR logo; optional styles available.
- Smooth transitions and straight-through components maximize performance by reducing restrictions.
- Strikes the perfect balance of power, sound, style, and quality for enthusiasts.
- Fully emissions compliant for worry-free operation.
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.9 ★★★★★
Based on 28 reviews
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Product Reviews
★★★★★ 5
ABSOLUTELY A MUST for Omegaverse Girls!!!
I ABSOLUTELY LOVE Jillian West and her books!!! I’m so happy I already bought book two and now I have to buy the others for the Assurance Security series!!
Not gonna lie Val kind of annoyed me at the beginning but she grew on me!! Her men are chef’s kisses!!! Holt annoys me some but I can let it slide. I already bought part two so I’m going to be reading that in between work phone calls!!!! DON’T TELL MY BOSS 😂😂😂😂
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Reviewed in the United States on September 30, 2025
★★★★★ 4
Baby bumps and bodyguards
Format: Kindle
Dark, emotional, and unexpectedly tender, Not Ready is an omegaverse romance that delivers found family feels, fierce protectiveness, and a very pregnant heroine who refuses to break. Vale’s on the run from a stalker, but lands in the arms of three private security alphas, cue the swoony tension, fake marriage twist, and slow-burn heat.
It’s a little gritty, a little soft, and a whole lot addictive. If you love protective alphas, high stakes, and heroines with quiet strength, this one’s a must-read.
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Reviewed in the United States on December 18, 2025
★★★★★ 5
Strong Omegaverse Comfort and a Attention Grabbing Plot
Format: Kindle
Jillian West never misses when it comes to Omegaverse, and Not Ready is no exception. This story was the perfect blend of cozy comfort and emotional depth while still delivering a strong plot.
Vale is such a powerful heroine, she is strong, capable, and determined but I love that she still allows her pack to love and take care of her. It’s that balance of independence and vulnerability that makes her so relatable.
The relationship dynamics were amazing: Bishop is steadfast and completely head over heels, Mercy is skeptical but protective in his own way, and Holt is the hesitant one whose slow fall is so satisfying to watch unfold.
The romance hits that sweet spot between insta-love and cautious build, keeping me hooked the entire way through. And that ending. Oh my god, the cliffhanger! I need the next book in this duet immediately.
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Reviewed in the United States on August 28, 2025
★★★★★ 5
Interesting
Format: Kindle
So I will say I enjoyed the story, for sure had its moments where it dragged but it was a great story. I really liked that omegas picked their alphas/make the pack. Normally the Alphas make it and the omega fits in with them which is great but I enjoyed this new version where all the power basically went to the omega. It was a nice change of pace. I can admit some of the weird bedroom stuff with her being pregnant was odd, it’s really not hard to do stuff when pregnant (I know I’ve had two and it’s normal and even encouraged at the end especially if you want the baby out). But I like the story as a whole and will read the second, I do hope the next one isn’t dragged bc it stopped being action or tense after she met her alphas and I don’t think it was brought up or properly done when they tried to do it. More sweet after she left.
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Reviewed in the United States on November 11, 2024
★★★★★ 3
I’m a little disappointed.
Format: Kindle
I usually like Jillian West’s books but this one was missing a lot for me. The pregnancy didn’t come across as real. She’s on her feet for 12 hour days but is perfectly healthy at 8 months pregnant? Yet the week she moves in all of a sudden she’s not? She is planning on actually running during one of the plot buildups. But at 8 months pregnant that’s incredibly hard to do. The lack of breathing ability and lung space, the change in body center, mass, and gravity. All of it prohibits running, unless you’re an athlete this didn’t come off as at all realistic.
I didn’t feel any connection with the alphas. There wasn’t any emotional connection. It could be because of the tense it was written in. But I didn’t get any deep feelings out of this. It came across as checking off boxes. Even the spicy scenes weren’t really believable for me. I wanted to see them fall for her, and it just kind of all fizzled. Even Bishop.
One thing I did really like was the ending. I did not see it coming and I’m interested in reading book two because of it. But on the whole this book was mostly disappointing for me.
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Reviewed in the United States on March 16, 2024
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