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  4 Reviews
USD 154.99
Part #: MBGMS9421

MBRP GMS9421 4" XP Series Front Pipe

2006-2007 GM 6.6L Duramax LLY/LBZ
Part #: MBGMS9421
  4 Reviews
$ $154.99
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The MBRP GMS9421 4" XP Series Front Pipe is constructred from T409 stainless steel and is designed for use on your 2006-2007 GM 6.6L Duramax LBZ. Designed for use with 4" exhaust systems. 

  • 4" Front Pipe
  • Mandrel Bent & Jig Manufactured 
  • T409 Stainless Steel Construction
  • Lifetime Warranty 


  • MFG. Number GMS9421
  • Manufacturer Name MBRP Inc.
  • Shipping Weight 25.00 lb.
  • Shipping Length 65 in.
  • Shipping Width 12 in.
  • Shipping Height 10 in.
  • UPC 882963100665
  • Warranty Yes
  • Warranty Info Lifetime
  • Prop 65 WARNING: Cancer & Reproductive Harm -


Nice Sound
Oil Burner
Location: Midwest
Once i got the cat cut off it was easy 2 install. Took about an hour. Truck is alot louder and the turbo spools alot faster. Sounds good
Front Pipe
Location: Pittsburgh
This is a great addition to your cat-back exhaust. Removes cat and opens up the exhaust for an awesome turbo wine. So easy to install, installed this in my driveway in 15 mins. Every diesel on the road should have one. I also talked to the Chevy dealer, it is totally road legal as diesels do not require emission testing in PA. Don't forget to block your egr and install a "finger stick" for added performance
Front Pipe Addition
Location: Unknown
I just got done installing the front-pipe into the exhaust system. I was able to modify it a little to fit the Banks Cat-Back system. Immediately I noticed the faster spool up time and the increase in power. However, the best noticeable increase was in the fuel economy. I had a PPE tuner, Banks intake, and Banks Cat-Back and was getting 16.8 mpg. Now with the addition of the front-pipe, I am averaging 21.1 mpg!!! Definitely the best upgrade to buy for the price! I recommend this to all diesel truck drivers.
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Questions and Answers

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Most Popular Questions

I would like to install this pipe just to eliminate my cadillac converter hook it on to my factory exhaust. Is this what I need?
View Staff Answer 
The MBRP STAINLESS STEEL FRONT PIPE #GMS9421 can be used to remove the catalytic converter from the truck, however this pipe is 4” and your factory is 3.5”. You may require an adapter to make this work 100%. Give our experts a call for assistance 1(888)343-7354!
What size is the pipe?
View Staff Answer 
the MBRP GMS9421 4" XP Series Front Pipe is a 4". It's intended for use with aftermarket exhaust systems because it has a flared end, to slip over other aftermarket 4" exhaust systems. Give our Diesel Experts a call at 1-888-343-7354 so we can assist you with building your custom exhaust.
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.