304 Stainless Steel with Stainless and Ceramic Packing
Highest quality materials to ensure long-life
4 Sound Modes in 1 Performance Muffler
1 muffler that adapts to your driving style
Simple Wireless Button Control
Most advanced wireless control for all modes
Engineered for the best sound profiles and performance
Advanced technolgy used to innovate design

Revolutionize your air-cooled driving experience.

The GTk Active Muffler Line from Ächtung Kraft is designed to deliver unparalleled performance and personalized choice in the sound you want to hear from your Air-Cooled Porsche 911 Flat-Six 911, 914, 964 and Carerra. 

2-IN GTk Active Muffler Line

2-IN Center Exit

11" RS width

This version delivers the same performance and sound quality of our original GT3 style GTk Muffler with an 11" Wide RS Style Center exit. 

4 distinct, active sound levels allow you to tailor your driving experience to match your mood and driving conditions.

2-IN Center Exit

GT3 width

Our original style of GTk Active Muffler with a sleek and sporty GT3 style center exit design and 4 modes of active sounds at the touch of a button. This muffler started the GTk line after 3+ years of development and testing to deliver amazing sound for your flat-six.

2-IN GTk Muffler Test Drive Videos.

Hear the amazing flat-six sounds that the GT/k delivers

One Muffler Delivers 4 Distinct Levels of Sound

Engineered to deliver the sound of four mufflers in one product.

Don't settle for a one trick muffler. The GTk line allows you to select the mode that fits your driving mood

Each active mode is tuned to keep a more mild idle, while unleashing the sounds when the revs climb. With the ability to switch between TOURING and SPORT (with the silencers insert) or REBEL and ROWDY (no Silencers), Porsche enthusiasts can enjoy a versatile and dynamic auditory experience, progressively increasing in aggressiveness and loudness - all from a single muffler.

Touring mode delivers a sporty exhaust note that is great for everyday drives.

Sport mode delivers a satisfying growl and increased volume ideal for spirited driving on winding roads.

With no silencers, the sound gets agressive,

becoming deeper and louder.

Our loudest option and highest flowing mode produces

race car sound and performance.


We didn't settle duplicating 50 year old designs. Instead, we leveraged advanced technology to create a whole new solution to the air-cooled muffler design

In-depth CAD & CFD design process

Advanced design technology delivers new advancements in muffler design

State-of-the-art analysis, coupled with thousands of miles of road testing, created the perfect blend of performance and sound quality

At Achtung Kraft, we believe in harnessing the power of cutting-edge technology to design the best mufflers. That's why we utilize advanced Computational Fluid Dynamics (CFD) and Computer-Aided Design (CAD) techniques throughout our design process. By leveraging CFD simulations, we analyzed airflow and optimized the internal structure of our mufflers to maximize performance and efficiency. With CFD and CAD - and thousands of road testing miles - we confidently say that our mufflers are not only visually stunning, but also deliver unmatched performance and sound quality on the road.

Rebuildable Silencer Technology

We perfected a silencer insert to provide better sound options

Advanced silencer design helps reduce noise while maintaing performance

With the ability to easily remove and replace the silencer, you can fine-tune your exhaust system's sound profile to suit your preference. Our rebuildable inserts are crafted from high-quality 304 stainless steel and quality ceramic packing, ensuring durability and longevity for years to come. And if they ever need a refresh, the design allows a simple and easy rebuild with new ceramic packing.

Engineered for maximum power and torque

Similar power across all GT/k Active Muffler modes

GT/k vs. Open Headers = less than 8HP difference on a built 3.6


Similar horesepower & torque across all active muffler modes // 3.6 


Delivers wireless on-demand control of the GT/k sound modes

Our control module gives you fingertip control of modes with the flip of a wireless switch

Easy to wire control module just needs (+)Power and (-)Ground and it manages the rest. On start-up the module ensures the valves are all closes for the quietest startup. A wireless, battery operated remote can be mounted anywhwere that triggers the muffler modes with the flip of a switch.With our control module, you can customize your exhaust system's sound to match your mood and driving conditions, ensuring that every journey is tailored to perfection.

The 2-IN GT/k Active Muffler line gives you all the sound options of 4 mufflers, in one compact package

Our GT/k line of mufflers is the first in the industry to give you so many sound options in one compact design. Your search for the perfect muffler sound is over when you have 4 sound options at your fingertips - all in one muffler.


Ultra high-performance option for all Flat-Six Motors

Mount Style
GT3 Center Out // SSI Flange Mount
11" Wide RS Tips // SSI Flange Mounts
GT3 Center Out // V-Band 2.5inch // For Custom Installs




Mounting Styles for 2-IN exhaust manifolds

SSI Flange Mount

SSI Flange Mount (headers)

V-Band (custom headers)

TheGT/k Active Muffler from Achtung Kraft – the perfect addition to your classic Porsche. This high-performance muffler is designed to optimize your Porsche's performance using the latest active muffler technology, while retaining the classic air-cooled Porsche sound that you know and love. Its active valve system allows you to adjust the exhaust note, giving you a deep, rich tone when closed, and an aggressive race car-inspired sound when opened. It's the ultimate way to enhance your Porsche's performance without sacrificing its iconic sound. Our Active GT/k Muffler offers FOUR distinct sound profiles to ensure that drivers have the flexibility to tailor their vehicle's sound to any occasion, driving style, or personal preference. We have tuned each mode to keep a more mild idle, while unleashing the sounds when the revs climb. With the ability to switch between Touring/Sport (with the silencer insert) or Rebel/Rowdy (no insert), Porsche enthusiasts can enjoy a versatile and dynamic auditory experience, progressively increasing in aggressiveness and loudness, all from a single muffler.

TOURING // CLOSED - with Silencer

The Touring sound profile is tailored for those seeking a refined and sophisticated exhaust note. It provides a mellow and subtle sound, allowing for a comfortable and relaxed driving experience. It is perfect for daily commuting, long highway drives, or occasions when a discreet and elegant exhaust note is desired. Touring mode delivers a sporty exhaust note that is great for everyday drives.

SPORT // OPEN - with Silencer

The Sport sound profile offers a more dynamic and spirited exhaust tone, enhancing the driving experience with a noticeable presence. It provides a deeper and throatier sound, amplifying the engine's performance characteristics when over 2k RPM. Sport mode delivers a satisfying growl and increased volume compared to the Touring mode, ideal for spirited driving on winding roads, or when desiring a more engaging driving experience.

REBEL // CLOSED - NO Silencer

For those seeking a more aggressive and attention-grabbing exhaust note, the Rebel sound profile delivers an assertive and powerful tone. It combines a deep rumble with increased volume, making a bold statement and turning heads wherever you go. Rebel mode is suited for those who want their Porsche to be noticed, and prefer a strong and captivating sound, while still maintaining a refined edge.

ROWDY // OPEN - NO Silencer

The Rowdy sound profile represents the pinnacle of intensity and performance-oriented sound. On throttle, it unleashes an aggressive and thunderous exhaust note that demands attention and announces your arrival. Rowdy mode delivers an exhilarating symphony of sound, providing an experience for those who seek the ultimate in auditory excitement. It is perfect for spirited drives, Rallyes, track days, or anytime you want to showcase the raw sound of your flat-six.

Disclaimer: Please note that our products are designed and intended for off-road use only. The use of our products on public roads and highways is prohibited by law in many areas. It is your responsibility to ensure that the use of our products complies with all applicable laws and regulations in your area. Any use of our products on public roads and highways is at your own risk and could result in damage to your vehicle, injury or even death. By purchasing and using our products, you acknowledge that you have read and understood this disclaimer, and you accept all responsibility and liability for any consequences that may arise from the use of our products.

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