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USD 559.99
Part #: MBS6004AL

MBRP 4" Installer Series Downpipe-Back Exhaust System S6004AL

2001-2004 GM 6.6L Duramax LB7 (All Crew & Extended Cabs)
Part #: MBS6004AL
★★★★★ ★★★★★ 9 Reviews
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The Best Systems Start with the Best Materials
Give your 2001-2004 GM 6.6L Duramax LB7 increased flow and performance with the MBRP 4" Installer Series Downpipe-Back Exhaust System S6004AL. Built from heavy duty aluminized steel our Installer Series performance exhaust systems offer a value price without compromising on the quality built into every component. While the seams are a major point of rust through with some budget systems our fully sealed tubing adds years to your system. Constructed to the same specifications as our top of the line Pro Series we back this line with an industry leading 3 Year Warranty.

Built to Perform 
You count on your truck to tow all of your gear to where you want it. With your MBRP performance exhaust you can make that happen with up to 18 HP more horsepower and 28 ft/lb more torque. Give your truck more pulling power and much improved throttle response with an MBRP diesel exhaust system. Our systems are so much more efficient, it will be easy to see what your truck can really do. 

Minimize Backpressure
The secret to getting more out of your diesel engine is to give it lots of cool, clean air. The only way that you can get fresh air in is to get the hot air out. From the spiral louvered high flow muffler to the fully mandrel bent tubing to minimal bend degree angles, your MBRP performance system gets exhaust out fast. Drop exhaust gas temperature by up to 200ºF and set the stage for all the performance you want. An MBRP performance exhaust system is the starting point to getting the most from cold air intakes, programmers, modules and downloaders. 

Easy Installation
MBRP systems are as much fun to install as to drive with on your truck. Bolt-on, no weld design makes installing this on your truck a no hassle one and a half to two hour project. Everything is direct fit to the OEM hangers and you get all the clamps and parts you will need, all in one box, no matter what configuration of truck you have.

Sound & Style 
Performance is one thing but at MBRP we believe that appearance and sound is just as important. Every MBRP performance exhaust system has been specifically tuned to get the optimal sound from your pickup. With our MBRP brand etched on the tip and our unmistakable styling, there's no question that you have the hottest exhaust on the road.

  • Rich, Mellow Exhaust Note
  • 4" Aluminized Steel Construction
  • Downpipe-Back Exhaust System 
  • Installs With Common Hand Tools 
  • Mirror Polished, T304 Stainless Steel Exhaust Tip
  • 3 Year Warranty
Application Note: 
All Crew & Extended Cabs applies to GM 2500HD/3500HD Pickups. Not for use on Cab & Chassis. 
This system will fit on Regular Cab models but requires the use and purchase of the Regular Cab Adapter Pipe below. 
Vehicles originally equipped with a catalytic converter must retain the factory catalytic converter. Removal of the catalytic converter may be a violation of federal or local regulations. 

Vehicle Applications

2001 Chevy 6.6L LB7 Duramax
2002 Chevy 6.6L LB7 Duramax
2003 Chevy 6.6L LB7 Duramax
2004 Chevy 6.6L LB7 Duramax
2001 GMC 6.6L LB7 Duramax
2002 GMC 6.6L LB7 Duramax
2003 GMC 6.6L LB7 Duramax
2004 GMC 6.6L LB7 Duramax


  • MFG. Number S6004AL
  • Manufacturer Name MBRP Inc.
  • Shipping Weight 76.00 lb.
  • Shipping Length 60 in.
  • Shipping Width 17 in.
  • Shipping Height 12 in.
  • Fuel Type Diesel
  • Diameter 4"
  • Exhaust Exit Single
  • Exhaust Type Downpipe-Back
  • Material Aluminized Steel
  • UPC 882963101808
  • Warranty Yes
  • Warranty Info 3 Year
  • Prop 65 WARNING: Cancer & Reproductive Harm -


★★★★★ ★★★★★
4.9/5 Stars out of 9 Reviews
(Unknown) | February 3rd, 2008
Very easy to install. You don't have to cut the factory exhaust if you can get the truck off the ground a little. It definitely takes a second pair of hands. Everything for the new exhaust slides into place, and looks great complete. Especially with the tip. It's not quite as loud as I had hoped/expected, but it should be flowing the exhaust gases a lot better. Nice, inexpensive, system.
4 in mbrp
(Unknown) | August 21st, 2008
very nice exhaust system sounds great very clean sound. make sure to double check every thing twice before tightening anything! thanks
4in Straight Piped Dmax
(unknown) | August 29th, 2008
This product exceeded my expectations. Sounds great. I bought both the front down pipe and the muffler delete pipe. It was very easy too install. Everything went together very well. Took me @ 2 hours in my driveway. I will definitely buy MBRP from mow on.
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Questions and Answers

Will the 4" installer turbo back system fit the stock downpipe? lb7 exhaust system
View Staff Answer 
Yes, the MBRP 4" S6004AL is designed to bolt right to your factory downpipe.

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Emissions Notice

This product is not legal for sale or street use in California. Certain aftermarket products are subject to governmental emission standards regulated by the California Air Resources Board. In order for these products to be legal on a specific vehicle in California, the part number must receive a CARB Executive Order (EO) number. This number makes the part legal for use only on specific years, makes and models of vehicles. A decal with CARB EO number for these parts must be displayed in the engine bay to satisfy smog inspection requirements.