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Hey guys i have a 2013 gs 3LT 6speed with npp. So i bought the car used. Whoever owned the car before be was a dummy apparently. The exhaust actuators aren’t hooked up and the are squares cut i to the side of the mufflers. I was wondering if and one knew what the squares were for and maybe a diagram to follow on the bimode so i can hook them back up since I bought a mild to wild switch and plan on putting headers on eventually
Can you take a picture of the "squares cut"? The cuts on the side of the muffler sounds like the stock muffler mod, which is a popular mod for those that don't have NPP and want a little more volume from the super quiet stock base mufflers.
Also 3LT does not indicate if the car came with NPP from the factory or not. You will need to look at the codes in the glove box for "NPP".
I would think a 3lt would but what am i looking for
NPP was an option on the base and GS, regardless of package.
Sounds like someone added pre-2011 Z06 mufflers that were cut open for the "muffler mod" which makes them slightly louder. For whatever reason, they never bothered to install "NPP in a box" or their own solution to actually have a working "NPP system".
Do your mufflers have the actuators on them? I would check the rest of the exhaust system to see if it's LS3 or if someone swapped in an LS7 exhaust.
muffler actuator
LS2/3 exhaust manifold on the right / LS7/9 exhaust manifold on the left
Another muffler shot where you can see the actuator
Last edited by 96GS#007; Feb 12, 2018 at 02:04 PM.
For some reason I can’t insert pictures from my phone. So I have big squares cut out on the inside of each of my mufflers. I know I have a z06 npp and someone removed two of my four cats. I looked on my glove box and did not see npp on there. Is that what the actual code is?
For some reason I can’t insert pictures from my phone. So I have big squares cut out on the inside of each of my mufflers. I know I have a z06 npp and someone removed two of my four cats. I looked on my glove box and did not see npp on there. Is that what the actual code is?
Yes the RPO code would show NPP for performance exhaust.
For some reason I can’t insert pictures from my phone. So I have big squares cut out on the inside of each of my mufflers. I know I have a z06 npp and someone removed two of my four cats. I looked on my glove box and did not see npp on there. Is that what the actual code is?
Being an older muffler, they likely swapped your old intermediate pipe with the two additional cats for the factory Z06 H pipe that doesn’t have cats.
Bottom line is that someone removed the stock LS3 exhaust and replaced it with an older Z06 bi-modal exhaust. Compare your exhaust manifolds to the pic I previously posted and you’ll know for sure.
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NPP exhaust help
