2017-2025 6.6L GM Duramax L5P 3.5"Downpipe Exhaust

System Specifications & Material

Q1: What’s the difference between 4-inch and 5-inch exhaust systems for diesel trucks?

• 4-inch Systems: Ideal for stock to moderately tuned engines. This diameter maintains the necessary backpressure to optimize low-end torque, making it the perfect choice for daily driving and consistent towing.
• 5-inch Systems: Designed for high-horsepower performance builds. These systems maximize exhaust flow to aggressively lower Exhaust Gas Temperatures (EGTs) and unlock peak power for racing or extreme heavy-duty applications.

Q2: Can a magnet stick to this exhaust pipe? Is it genuine stainless steel?

• Yes. This pipe is crafted from T-409 Stainless Steel. Unlike 304-grade (non-magnetic), T-409 is a magnetic alloy specifically engineered for automotive exhaust environments. It offers a superior balance of corrosion resistance, high-temperature durability, and cost-effectiveness compared to aluminized steel.

Q3: How thick is the exhaust pipe, and what’s its service life?

• The pipe features a heavy-duty 14-gauge (approx. 2mm) wall thickness. Built from durable T-409 stainless, it is engineered to withstand extreme exhaust heat and off-road vibrations for years of rust-resistant, reliable use.

Fitment & Compatibility (LML Duramax)

Q4: Is this a full Turbo-Back system or a Downpipe-Back system?

• This is a Downpipe-Back system. It replaces all exhaust components starting after the factory downpipe, including the restrictive DPF and stock piping. To achieve a true "Turbo-Back" setup, an aftermarket performance downpipe is required in addition to this kit.

Q5: I have a 2015 Duramax—how do I ensure I choose the right kit?

• The 2015 model year was a "split" year for the LML Duramax. You must verify your truck’s downpipe connection type:Early 2011–2015 Models: The exhaust downpipe attaches via a V-band clamp.Late 2015.5–2016 Models: The exhaust downpipe uses a 3-bolt flange connection.
• Please confirm your specific connection design to ensure a perfect bolt-on fit.

Q6: Is this pipe compatible with my LML if I upgrade to a 5-inch exhaust?

• Absolutely. This component is engineered to be fully compatible with both 4-inch and 5-inch performance exhaust configurations. It is a top-tier choice for 2015–2016 LML owners looking to maximize exhaust scavenging and overall engine performance.

Performance & Legal Compliance

Q7: Will a DPF delete kit boost my truck’s performance?

• Yes. By removing the factory restrictions, you will experience:Lower EGTs: Essential for protecting engine components under load.Faster Spool: Improved turbocharger and throttle response.Better MPG: Increased fuel efficiency (when paired with proper ECU tuning).Reliability: Permanent elimination of DPF clogging and costly "Regen" cycle failures.

Q8: Can I legally drive my truck with a DPF delete on public roads in the US?

• Off-Road / Racing Use Only. Removing the Diesel Particulate Filter (DPF) is a violation of U.S. EPA and CARB emissions regulations. Use on public highways may result in significant fines, failed emissions inspections, and legal penalties. Always verify your local and state laws before installation.

Q9: Do I need a tuner after installing this exhaust?

• Yes. Modifying the DPF system on a Duramax LML requires a "DPF-off" tune (e.g., EFI Live or EZ Lynk). Without a proper tune, the truck will trigger a Check Engine Light (CEL) and enter "Limp Mode."

Shipping & Delivery Policy

At DieselPerf, we specialize in high-performance diesel emission system accessories. Our mission is simple: to deliver the parts you need with maximum efficiency, security, and transparency. Below are the guidelines we follow to ensure your order reaches you safely.

1. Perfecting Your Delivery

To ensure a seamless experience and avoid unnecessary surcharges, please keep the following in mind:

• Precision Matters: Always verify your shipping address at checkout. Accurate data prevents costly rerouting fees.
• Address Classification: Carriers determine rates based on zoning. If your business is located in a residential area, it will be classified and billed at the Residential Delivery rate.
• Stay Reachable: Please provide a valid phone number. Carriers often need to coordinate delivery windows; missed connections can lead to significant delays.

2. Order Consolidation

To get your parts to you as fast as possible, we ship items as they become available. This means your order may arrive in multiple packages. Rest assured, you will never be charged extra for these split shipments.

3. Our Logistics Network

We partner with world-class carriers, including UPS, FedEx, DHL, USPS, and Amazon Logistics.

• Global Fulfillment: We fulfill orders from our strategic hubs in the U.S. and Hong Kong, prioritizing the location closest to you.
• Lead Times: While most orders arrive within 5–15 business days, specialty items or factory-direct shipments may require additional transit time.

4. Damaged or Missing Shipments

Your satisfaction is our priority. If your order arrives compromised, please follow this protocol:

For Damaged/Incomplete Deliveries:

1. Document Immediately: Note any visible damage or missing pieces on the delivery receipt before signing.
2. Contact Us: Reach out within 2 business days at service@DieselPerf.com or via phone at +1 325-013-1608 / +852 5381 0098.
3. Preserve Evidence: Keep all original packaging and take clear photos of the damage to expedite your claim.

For Lost Shipments:
If a package goes missing, we will initiate a dock check with the carrier (typically taking 2–7 business days). If the items cannot be located, we will work with you to provide a full replacement or a refund.

5. Estimated Timeframes

• Processing: Orders are generally dispatched from our warehouse within 1–2 business days.
• Transit: Standard U.S. ground shipping typically takes 7–10 business days, though many items arrive sooner.
• Holiday & External Factors: Please account for seasonal peaks (Christmas, Thanksgiving, etc.) and unforeseen "Force Majeure" events like extreme weather, which may naturally extend delivery windows.

Customer Support

Our team is here to help you get back on the road.

• Hours: Monday – Friday | 9:00 AM – 6:00 PM
• Email: service@DieselPerf.com

All Dieselperf products enjoy a 1-year limited warranty starting from the date of goods receipt, covering defects in product materials and workmanship.

Warranty Coverage

This warranty only covers failures arising from original material and manufacturing defects under proper installation and normal use. The warranty is non-transferable and exclusively available to the original buyer. An order number or valid purchase receipt is mandatory for warranty claims.

Warranty Exclusions

The 1-year limited warranty does not apply to the following circumstances:

• Normal wear and tear and surface scratches generated during regular use
• Damage caused by improper installation, unauthorized disassembly or modification
• Damage resulting from misuse, accidental impact, negligence and natural disasters
• Natural aging loss of consumable spare parts
• Labor costs incurred from product disassembly, assembly and maintenance

Warranty Claim Process

1. Submit Application: Email customer service with your order number, detailed fault description and clear photos or videos of product defects.
2. Claim Review: Our technical team will verify the issue. Additional information or product return inspection may be required.
3. Settlement Solutions: Upon claim approval, we reserve the right to take one of the following measures:

• Repair the defective product
• Replace with a brand-new authentic item
• Deliver compatible replacement parts for repair

Limitation of Liability

Within the scope permitted by law, Dieselperf shall not be responsible for any special, incidental, indirect or consequential losses, including but not limited to profit losses, business suspension losses and other economic damages.