The ARM Motorsports 6" B58 Catted Downpipe is engineered for enthusiasts who want maximum performance gains with reduced emissions and without the odor associated with catless systems. Featuring a massive 6-inch, 200-cell high-flow ceramic catalyst, this downpipe greatly improves exhaust flow, turbo response, and overall power on all B58-equipped BMW and Toyota Supra models. It retains the aggressive sound, fast spool, and performance advantages of a catless downpipe while offering a cleaner, more refined emissions profile.

By replacing the restrictive factory downpipe, this 6" catted unit enhances horsepower and torque potential and supports Stage 2+ tuning reliably. The upgrade also increases exhaust volume, sharpens turbo spool noise, and improves exhaust tone even on the OEM tune.

Constructed with a precision CNC-machined 4.5-inch V-band turbo flange, the downpipe ensures perfect alignment with the OEM or OEM-style upgraded turbochargers. Oxygen sensor bungs are positioned for optimal accessibility: the pre-cat bung is closer to the turbo to prevent sensor strain, while the post-cat bung includes an integrated extension for proper reach around the 6-inch body. A flex section is incorporated to reduce stress on the turbo during hard driving, and the unit mounts securely using the OEM two-bolt bracket.

Compatible with factory and aftermarket midpipes, the ARM 6" B58 Catted Downpipe provides a durable, high-performance foundation for any B58 build focused on power, drivability, and reliability.

Fitment:

Fits the following B58 3.0L models:

BMW

• F22 M240i
• F22 M240i xDrive
• F23 M240i
• F23 M240i xDrive
• F30 340i
• F30 340i xDrive
• F32 440i
• F32 440i xDrive
• F33 440i
• F33 440i xDrive
• F34 340i xDrive
• F36 440i
• F36 440i xDrive
• G30 540i
• G30 540i xDrive
• G32 640i
• G32 640i xDrive
• G12 740i
• G12 740i xDrive
• G15 840i
• G15 840i xDrive
• Toyota
• A90 Supra (B58)
• A91 Supra (B58)