Wehrli WCF100304-GB 2011-2016 LML Duramax 4in Stage 2 Intake Kit with Air Box Gloss Black Made in USA

WCF100304-GB is the complete Stage 2 cold air intake solution for 2011-2016 6.6L Duramax LML trucks. Built at WCFab's facility in DeKalb, Illinois, every component in this kit is fabricated and powder-coated in-house using American materials and American craftsmanship. The result is a bolt-on intake upgrade that delivers a flow-bench-verified 37% improvement in airflow over the stock intake system, equivalent to approximately 250 CFM of additional air at peak flow, with no ECU tune required.

Made in the USA at WCFab's DeKalb, Illinois facility. Powder coating is performed in-house using their state-of-the-art coating system.

What Makes Stage 2 Different

Stage 2 includes everything in the Stage 1 kit (WCF100194) plus the 4.8" CNC machined cast aluminum high-flow turbo intake horn, an O-ring seal for the turbo inlet, and new EGR gaskets. The 4.8" inlet diameter is the largest LML intake horn on the market, adding a further 5.6% airflow gain over the stock OEM horn.

Stage 1 vs Stage 2 Comparison

What's Included

• 4" mandrel-bent fabricated aluminum intake pipe (14-gauge aluminum)
• Aluminum air box with lid (10-gauge sheet aluminum)
• Dry air filter with 4" inlet
• Outerwears hydrophobic pre-filter cover
• 4.8" high-flow CNC machined cast aluminum turbo intake horn
• Silicone boot (couples intake pipe to intake horn)
• Stainless steel T-bolt clamps
• Installation hardware (all fasteners)
• O-ring seal for turbo inlet
• New EGR gaskets (front section to rear section)
• New EGR bypass pipe gaskets
• Humidity sensor port block-off plate
• MAF sensor mounting screws (2x, for transferring MAF to new intake pipe)

Performance Gains

• 37% improvement in airflow over the stock intake system (approximately +250 CFM at peak flow)
• 5.6% improvement in airflow over the stock intake horn from the 4.8" cast aluminum horn
• Improved horsepower and torque across the RPM range
• Quicker throttle response and improved turbo spool-up
• Cooler intake temperatures via sealed air box drawing from the inner fender cold air stream
• No power adder or turbo upgrade required to realize gains

Product Specifications

Vehicle Fitment

Fits 2011-2016 Chevrolet and GMC heavy-duty trucks equipped with the 6.6L Duramax LML diesel engine.

Installation Overview

Bolt-on installation using only basic hand tools: 10mm socket, 13mm socket, and a flathead screwdriver. No cutting, welding, or tuning required. The 37-step installation process involves removing and reinstalling the EGR cooler and EGR valve to properly seat the new intake horn, then transferring the MAF sensor and CAC temperature sensor to the new intake pipe.

Important: 2011 model year trucks must update the PCV Regulating Valve to 2012-2016 model year specification prior to installation.

Compatibility Restrictions

• NOT compatible with aftermarket LML Y-bridges that relocate the manifold inlet from the original factory driver-side location.
• Air box NOT compatible with intake pipes from kits WCF100337, WCF100689, or WCF100691.
• 2011 model year: PCV Regulating Valve must be updated to 2012-2016 spec before installation.

Frequently Asked Questions

Will this fit my 2011 LML Duramax without modifications?
Yes, with one requirement: 2011 trucks must update the PCV Regulating Valve to 2012-2016 specification before installation. Once that is done, the install follows the standard 37-step process with basic hand tools.

Do I need a tune after installing this intake?
No. The 6.6L LML Duramax ECU adjusts for increased airflow automatically. No tune is required to realize the 37% airflow gain.

What is the difference between Stage 1 and Stage 2, and which should I buy?
Stage 1 (WCF100194) includes the 4" pipe, air box, dry filter, and hardware. This Stage 2 kit adds the 4.8" CNC cast aluminum intake horn, O-ring turbo seal, and EGR gaskets. Stage 2 delivers an extra 5.6% airflow gain and saves you $ compared to buying Stage 1 and the horn separately.

Is this compatible with upgraded turbos?
Yes, with OEM VGT and drop-in VGT style turbo upgrades. Not compatible with aftermarket Y-bridges that relocate the manifold inlet from the factory driver-side location.

Will this void my factory warranty?
Under the Magnuson-Moss Warranty Act (15 U.S.C. Section 2301 et seq.), a manufacturer cannot void your entire vehicle warranty solely because you installed an aftermarket part. They can only deny coverage for a specific failure if they can prove the aftermarket part caused it. Consult your dealer if warranty status is a concern.

Is this CARB compliant or legal in California?
No. This product is not for sale in California and has no CARB Executive Order number.

What warranty does WCFab provide?
WCFab covers this kit under a 12-month Limited Product Warranty from date of original purchase. Non-transferable. WCFab will repair or replace defective components at their discretion. A Return Authorization number is required before sending any product back.

How does the sealed air box improve intake temperatures?
The aluminum air box draws air through the inner fender opening, pulling cool ambient air from outside the engine bay rather than hot underhood air. This provides a consistent cold-air charge regardless of engine bay temperatures.

Available Colors

This Stage 2 kit is available in over 30 powder coat colors. Standard quick-ship colors include Gloss Black (this listing, WCF100304-GB), WCFab Red (WCF100304-RED), WCFab Grey (WCF100304-GRY), Gloss White (WCF100304-GW), and Candy Teal (WCF100304-CT). Custom and upcharge colors are available with a 10-15 business day lead time.

Emissions and California Notice

Not for sale in California. This product is not CARB legal and cannot be used on any motor vehicle operated on public roads in the State of California.

WARNING (California Proposition 65): This product can expose you to chemicals including lead and its compounds, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, visit www.P65Warnings.ca.gov.

Warranty Summary

WCFab Limited Product Warranty: 12 months from date of original purchase. Covers defects in materials and workmanship. Non-transferable. WCFab will repair or replace the defective product at their option, not to exceed the original purchase price.