Description
Overview
The Flowmaster Flow FX Cat-Back Exhaust System is engineered for the 2020-2025 GM 2500HD/3500HD trucks equipped with the 6.6-liter gas engine, delivering a factory-easy upgrade in flow, sound, and style. Built from durable 409 stainless steel throughout, this complete cat-back kit is designed to breathe better, sound stronger, and stand up to years of hard use behind your heavy-duty GM truck.
At the heart of the system is the Flow FX “straight-through” muffler, a 24-inch straight-through design that produces a moderate sound level while prioritizing maximum performance. On the dyno, this exhaust delivered gains of up to +9 horsepower and +10 lb-ft of torque at the rear wheels, giving your 6.6L gas HD a measurable bump in real-world usable power.
Better Flow, Real Gains
The system steps up from a 3.50-inch pipe into dual 3.00-inch mandrel-bent tubing, promoting smoother, less restrictive exhaust gas flow. Mandrel bending maintains consistent pipe diameter through every curve, so airflow stays strong from the cat-back connection all the way to the tips. The Flow FX muffler features a center inlet with dual outlets, each measuring 3.00 inches, feeding a true dual-exit layout.
Style That Matches the Performance
This system exits out both sides of the truck, behind the rear wheels, and is finished with 4.50-inch black ceramic tips for a bold, custom look. The tips carry an embossed logo for a clean, factory-plus appearance that complements the aggressive stance of your HD truck. Silver pipe and muffler finishes keep the whole system looking purposeful and durable.
Easy, At-Home Installation
Designed as a bolt-on upgrade, the Flow FX cat-back uses all the existing factory hanger locations, so there is no cutting, welding, or custom fabrication required. The kit includes installation instructions and all necessary hardware, making this a straightforward project you can complete in your own garage.
- 409 stainless steel construction throughout for lasting durability
- 3.50 to dual 3.00-inch mandrel-bent pipes for improved exhaust flow
- Flow FX straight-through muffler with a moderate sound level
- Dyno-proven gains up to +9 hp and +10 lb-ft at the rear wheels
- Dual side-exit design with 4.50-inch black ceramic embossed tips
- Uses factory hangers; includes hardware and instructions
Fitment & Compliance
This cat-back exhaust is built specifically for 2020-2025 GM 2500HD/3500HD trucks with the 6.6-liter gas engine. It is CARB (California) compliant and carries a California Proposition 65 warning. Backed by Flowmaster’s Lifetime Limited Warranty, the Flow FX system is a confident, performance-driven choice for your heavy-duty GM.
