Description
Overview
The Flowmaster Flow FX Extreme Cat-Back Exhaust System is engineered for the 2003-2024 Toyota 4Runner equipped with the 4.0-liter engine, delivering an aggressive exhaust note and a genuine boost in performance. Built around a Flow FX series muffler, this stainless steel cat-back setup is designed for drivers who want a deeper, more purposeful sound paired with improved flow and long-term durability.
At the heart of the system is 3.00-inch mandrel-bent 409 stainless steel tubing. The mandrel bends maintain a consistent internal diameter throughout every curve, allowing for maximum exhaust flow, while the 409 stainless construction stands up to heat, corrosion, and the demands of hard driving. On the dyno, this system produced max gains of 4 horsepower and 5 lb-ft of torque at the rear wheels.
Built for the Trail
What sets the Flow FX Extreme apart is its turndown-style, dump exit positioned right after the muffler. By eliminating the over-axle tailpipe entirely, the system improves ground clearance and departure angle — a meaningful advantage when you’re tackling more extreme off-road situations. Fewer components hanging past the axle means less to catch on obstacles and more confidence on the trail.
Key Benefits
- Aggressive Flow FX series muffler tuned for a bold, performance sound
- 3.00-inch mandrel-bent 409 stainless steel tubing for maximum flow and durability
- Turndown dump exit that removes the over-axle tailpipe for better ground clearance and departure angle
- Dyno-proven gains of 4 hp and 5 lb-ft at the rear wheels
- Single tailpipe configuration with a center muffler inlet and 3.00-inch outlet diameter
- CARB (California) compliant — Emission Code 5
Easy, Bolt-On Installation
This cat-back system is designed for a straightforward installation. It uses factory-mounting locations and includes all of the necessary hardware, so you can bolt it on using the existing factory hangers without cutting or fabricating custom mounts. The Flow FX muffler measures 40.00 inches overall with a center inlet and a 3.00-inch outlet, finished in a clean silver that matches the silver pipe color of the system.
Fitment
Purpose-built for the 2003-2024 Toyota 4Runner with the 4.0-liter engine. The complete kit includes the Flow FX muffler and single tailpipe with all mounting hardware.
Backed by Flowmaster’s Lifetime Limited Warranty, the Flow FX Extreme Cat-Back is a durable, off-road-minded upgrade that combines aggressive sound, added flow, and improved trail clearance in one bolt-on package. WARNING: This product can expose you to chemicals known to the State of California under Proposition 65.
