MBRP GM8427 3" Turbo Downpipe

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2011-2015 GM 6.6L Duramax LML
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MBRP Performance Exhaust
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The MBRP GM8427 3" Turbo Downpipe provides a smoother flow from the turbo in your 2011-2015 GM 6.6L Duramax. Removing the restriction in the factory downpipe results in lower EGT’s and increased performance. The down pipe is relatively easy to install due to the precision bends that you’ve come to expect from MBRP.


  • Greater Heat Retention
  • 20% Greater Flow Over Stock
  • Richer Diesel Sound 
  • Will Not Affect DPF or Urea System 
  • Gains of +21HP & +24 Ft-lbs.

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(46 Ratings, 1 Review) Average Rating:
Will not seal. Leaks diesel fluid.
Seth (Iowa) 12/4/2015 2:51 PM
The OEM removal is a pain in the a$$ but successfully installed MBRP downpipe. Did notice the power and torque went up slightly. THE MAJOR ISSUE HERE, the pipe leaks diesel fluid from the 9th injector. The truck was doing a regen when I noticed my truck smoking under the hood. I was close enough to a deal that I pulled the truck in and they got me right in. They knew right away what the issue was. It is a known issue that it can leak fluid even with the stock down pipe. That is also why there has been notices sent out from GM about it. If you check out the 2015.5 and up they have a 3 bolt gasket. So back to the dealership, I had them try to adjust the fitment to correct the issue. They tried and did a force regen and yet again it still leaks fuel. They request they factory downpipe to be reinstalled and luckily I held on to it. They installed it and also installed some sort of sealant between the downpipe and the upper pipe of the exhaust. I contacted MBRP and got a hold of Candice she was very nice to me. They requested I send the pipe back for inspection. I also supplied documentation from the dealership saying it doesn't fit to provide a proper seal. I also supplied pictures and documentation to fix this problem. All of my input was pointless, because they didn't care. It took them A MONTH to get the pipe just to inspect it. I sent it back on the note that if it bet their standards I wanted my money. Well they said it meets their "fitment standards". So I had to pay $20 just to ship my pipe back to me. In conclusion I will not be buying from MBRP and I suggest no one buy this pipe if they have an OEM equipped truck. Even though it says it will work on a factory equipped truck.