It's quieter than my old magnaflow. Either that or a factory exhaust, but that would probably cost you a little flow. 
How to quiet down a GMMG exhaust??
Thread Starter
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Joined: Dec 2001
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From: Atlanta
How to quiet down a GMMG exhaust?? Got the 427 GMMG ZL1 back today and just as we thought the GMMG chambered exhaust sounds like open headers.....only louder!! Under any accelleration at all the sound could probably be heard for half a mile. We are going to up the boost to 10 psi when I take it back in a month so during that time I need to find out how some of you have fixed this problem. BTW - with 4 psi and initial tuning it put down 657 rwhp through a Moser 4.10. With 10 psi and 800+ rwhp it is only going to be worse.
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Originally Posted by grb
It is not streetable as is. I was wrong. There are no cats. This thing sounds like a NASCAR hot rod on steroids coming down the road!! Got to try a Borla cat back or something.
Thread Starter
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From: Atlanta
I don't know where the cats would fit? I do think I'll swap the SLP exhaust from my SS to the ZL1. If it will fit. Yeah, it's loud. Scares small children, aminals just run and women think the end of the world is coming.
Thread Starter
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From: Atlanta
I will probably try adding something after the y-pipe and go from there. I don't like driving around in a 100 degree car feeling like I've just robbed a bank hoping a cop doesn't hear or see me. It's not a relaxing way to drive.
if you have an ORY-pipe get CATS, and if thats not enough get a Bullit muffler (Dynomax, Borla XR-1, or even some other chambered mufflers ike Stainless Works, Sweet Thunder, etc.)
If you don't lik ehtat you don't deserve a car from GMMG! lol j/k...If you have the GMMG badge on your car, I'll take it if you don't like/want it
(i highly doubt that will happen 
)
If you don't lik ehtat you don't deserve a car from GMMG! lol j/k...If you have the GMMG badge on your car, I'll take it if you don't like/want it
(i highly doubt that will happen ) 
