Wehrli Custom Fab Wehrli Custom Fabrication 3.5" Down Pipe (WCF100129)
Fits 2017-2026 6.6L Duramax V8 (L5P)
We earn a commission if you buy through links on this page. Prices are the same for you. Full disclosure
A direct-fit downpipe for the Duramax diesel engine that connects right after the catalyst and bolts up to the factory front pipe, with a ceramic coating and heat wrap already installed.
why this one — This is Wehrli's own direct listing with a clear in-stock price and documented SEMA emissions-compliance (SC-WCF01-0183), so it is legal for street use without guesswork, unlike many diesel exhaust parts.
No manufacturer or independent dyno figure found. Wehrli states the pipe improves exhaust flow and that WCFab piping plus emissions-compliant tuning are recommended "for optimum performance gains," but no standalone HP/TQ number is published for the downpipe alone.
Cannot ship to California (manufacturer shipping restriction stated on product page).
No published gain figure for this part, and nothing here is a guarantee. Price is a list price and can lag the retailer; confirm at checkout. See how we check a price and our affiliate disclosure.