What is a cat-back exhaust system?

A cat-back exhaust system replaces the factory exhaust components from the catalytic converter back to the tailpipe. This includes mufflers and exhaust piping, and it's a common way to change the sound and performance of your vehicle's exhaust.

What kind of sound can I expect from the LoudMouth system?

The LoudMouth system is known for its aggressive and loud exhaust note. The straight-through muffler design minimizes restrictions, resulting in a much louder tone compared to stock mufflers.

Does this system require welding for installation?

Typically, cat-back exhaust systems like this are designed as bolt-on replacements and do not require welding. However, it's always best to refer to the manufacturer's installation instructions for specific details and any required hardware.

SLP 1999-2004 Ford Mustang 4.6L LoudMouth Cat-Back Exhaust System

Specifications

Brand: SLP
Part #: M31007
UPC: 871782000911

SLP 1999-2004 Ford Mustang 4.6L LoudMouth Cat-Back Exhaust System

Name: SLP 1999-2004 Ford Mustang 4.6L LoudMouth Cat-Back Exhaust System
Brand: SLP
Price: 645.12 USD
Availability: InStock

$645.12

On Backorder — Expected to ship by Apr 19, 2026

Order now to reserve yours — we'll ship as soon as stock arrives. Full refund if we're unable to fulfill.

Fits 1999-2004 Ford Mustang 4.6L. SLP LoudMouth cat-back exhaust system for an aggressive exhaust note.

Key Features

Fits 1999-2004 Ford Mustang GT and Mach 1 models with the 4.6L engine.
SLP LoudMouth cat-back exhaust system provides a notably aggressive and loud exhaust tone.
Modular design for potentially easier installation.
Straight-through muffler design helps minimize restrictions and improve exhaust flow.
Constructed from durable materials suitable for undercar applications.

⚠️ CA WARNING: This product can expose you to chemicals known to the State of California to cause cancer and/or birth defects or other reproductive harm. Learn more

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Fits this vehicle

Ford Mustang 1999-2004

Product Details

This SLP LoudMouth cat-back exhaust system is made specifically for your 1999-2004 Ford Mustang GT or Mach 1 with the 4.6L engine. If you're looking to give your Mustang a more aggressive, louder exhaust note that really lets people know you're coming, this system is a popular choice. It replaces the factory mufflers and exhaust piping from the catalytic converter back, changing the sound and flow characteristics of your exhaust.

SLP designed this system to be modular, meaning it's built in sections that connect together, which can sometimes make installation more straightforward. The LoudMouth name comes from the straight-through muffler design, which minimizes restrictions and allows for a more direct path for exhaust gases. This not only contributes to the louder sound but can also help with exhaust flow. The system is constructed from durable materials to withstand the underbody environment of your Mustang.

When installing a cat-back system like this, you're typically looking at a bolt-on process that doesn't require welding. It's a common upgrade for Mustang owners who want to enhance the sound of their V8 engine. Be aware that this system is designed for a loud sound, so if you prefer a more subdued tone, you might want to consider other options. Check the manufacturer's instructions for any specific installation details or hardware requirements.