Description
Overview
The Flowmaster Flow FX Cat-Back Exhaust System Kit is a straightforward, high-value performance exhaust upgrade engineered for 2020-2026 Chevrolet and GMC 2500HD and 3500HD trucks equipped with the 6.6L gas engine. Built to help you customize your GM truck to your personality, this Flow FX series catback exhaust delivers aggressive-yet-moderate tone paired with real, measurable performance gains — all with a bolt-on installation you can complete at home.
Constructed from durable 409 stainless steel, the muffler and inlet pipe are designed for years of trouble-free service under heat, road spray, and daily driving. A 3.50-inch inlet pipe feeds into the 409 stainless steel Flow FX “straight-through” muffler, promoting strong flow and an aggressive exhaust note while eliminating the interior drone that plagues so many aftermarket systems. The muffler then ties directly into the factory tailpipe, making this one of the simplest and most effective performance exhaust system upgrades you can add to your rig.
Performance & Sound
On the dyno, this exhaust system produced max gains of 11 horsepower and 10 lb-ft of torque at the rear wheels — power you can feel in improved acceleration and stronger towing performance. The straight-through muffler design keeps flow high and backpressure low, giving your 6.6L an aggressive presence at throttle without turning the cab into an echo chamber at highway cruise.
Key Highlights
- Flow FX cat-back exhaust system built from durable 409 stainless steel muffler and 3.50-inch inlet exhaust pipe
- Straight-through Flow FX muffler with center inlet and center 3.50-inch outlet for great sound and maximum flow with no drone
- Max dyno gains of 11 hp and 10 lb-ft at the rear wheels for better acceleration and towing
- Aggressive / moderate sound level with a silver pipe finish and natural muffler finish
- Uses all factory hanger locations and connections for an easy at-home install
- Includes installation instructions and all necessary hardware
- CARB (California) compliant and backed by Flowmaster’s Lifetime Limited Warranty
Fitment & Installation
This kit fits 2020-2026 GM 2500HD and 3500HD trucks with the 6.6L gas engine, and works with both 2WD and 4WD models. Because it mounts to all the factory hanger locations and connects to the stock tailpipe, installation is simple and direct — no cutting or custom fabrication required. Every kit ships with detailed instructions and the hardware needed to get the job done.
Whether you’re shopping for a performance exhaust that adds power and attitude or a clean, reliable upgrade over the restrictive factory setup, this Flowmaster Flow FX system delivers proven gains, honest stainless construction, and a warranty that stands behind it. Add the exhaust system that transforms how your GM truck sounds and performs.
