MAD BMW B58 2025+ Gen 3 M340 M440 Fat Boy 5.0" Downpipe Catless

Unleash the full potential of your 2025+ B58 Gen 3 with the MAD Fat Boy 5.0" Catless Downpipe. Crafted from premium 304 stainless steel, the larger 5.0-inch diameter delivers superior airflow for more horsepower, quicker turbo response and noticeable torque gains.

The expanded diameter sets it apart from standard catless downpipes with a deeper, richer and significantly more aggressive exhaust tone. Precision welds and exceptional craftsmanship ensure perfect, durable bolt-on fitment.

Features

• Premium 304 stainless steel.
• Expanded 5.0" diameter for maximum airflow.
• Deeper, richer, more aggressive tone with more power than standard catless designs.
• Precision craftsmanship and perfect bolt-on fitment.

Fitment

• 2025+ BMW M340 & M440
• 2025+ BMW X3 G45 M50
• 2025+ BMW X4 G46 M50

Emissions disclaimer: This product is not legal for sale or use on pollution-controlled vehicles operated on public roads and is intended for off-road, race, or closed-course competition use only. You are responsible for compliance with all applicable emissions laws; use on public roads may violate the Federal Clean Air Act (42 U.S.C. § 7522) and similar state laws. Please check your local laws before purchase and installation.

Ships from our Vancouver shop — KORE SPEED is proudly Canadian-owned, with no surprise cross-border duties for Canadian buyers. Questions on fitment? Email support@korespeed.com.