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Supplier details checked 2026-09-23 · Test catalog
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Fits 20-26 GM 2500HD/3500HD 6.6L Gas Engine FFX Direct Fit Muffler Exhaust System, 409 stainless steel
Flowmaster Flow FX Direct Fit Muffler
A tuned Flow FX style muffler delivers a deep, aggressive to moderate performance tone and improves exhaust flow with no drone
Kit includes complete hardware and factory styled hangers in the stock locations for an easy installation
3.5-inch mandrel bent 16-gauge 409 stainless steel tubing maximizes exhaust flow and improves durability
Max increases of up to 7 hp and 5 lb-ft over the stock exhaust at the wheels
Tuned performance muffler eliminates interior drone
Maintains factory warranty
Lifetime Limited Warranty
Flowmaster 20-25 GM 2500/3500 6.6L GAS Direct Fit FlowFX Muffler
2025 GM 25003500 66L GAS DIR FIT FFX
MUFF 20-26 GM 2500/3
Flowmaster's® Flow FX Direct-Fit Muffler exhaust system for the 2020-2026 GM 2500HD and 3500HD trucks with the 6.6L gas engines gives you a great value packed way to help you customize your GM truck to your personality. This performance muffler system fits both 2/4 Wheel drive models and is manufactured from 409 stainless steel for years of trouble-free service and performance. Features include a 3.50-inch inlet pipe leading into a 409 stainless steel Flow FX series "straight-through" muffler for great sound and maximum performance and no drone. The muffler then connects to the factory tailpipe for a simple and effective performance upgrade. Max dyno gains of 7 hp and 5 lb-ft at the rear wheels. This results in better acceleration and towing performance. The system uses all the factory hanger locations and connections for an easy installation that you can do at home. Kits include installation instructions and all necessary hardware. Backed by Flowmaster's Lifetime Limited Warranty.
MUFF DF ASMB
