Wehrli Custom Fabrication 100129 3.5" Downpipe for 2017-2025 Duramax L5P

The Wehrli Custom Fabrication 100129 is a 3.5-inch high-flow downpipe designed to replace the restrictive factory downpipe on 2017-2025 GM Silverado and Sierra 2500HD/3500HD trucks equipped with the 6.6L Duramax L5P engine. This emissions-compliant performance upgrade eliminates the crushed and pinched factory design that creates a significant exhaust flow bottleneck, especially under load or during towing.

Key Features:

• Full 3.5-inch diameter maintains consistent flow throughout the pipe
• High-temperature black ceramic coating for extreme heat resistance
• Pre-installed heat wrap for thermal protection and reduced underhood temperatures
• Direct bolt-in installation using factory 4-bolt flange connections
• Connects to DOC (Diesel Oxidation Catalyst) outlet and factory front pipe
• All sensor bungs pre-installed for proper emissions system compatibility
• No tuning required - emissions compliant upgrade
• Quality steel construction with professional-grade finish

This downpipe delivers improved turbo efficiency, quicker spool-up, and enhanced throttle response by eliminating the restrictive factory section. The smooth, full-diameter design allows exhaust gases to flow freely, reducing backpressure and maximizing performance potential. Perfect for trucks that tow heavy loads or as a foundation for future performance upgrades, the Wehrli 100129 provides measurable gains while maintaining full emissions compliance.