Jay
Muffler mod
Le Mans Master
Joined: Jan 2004
Posts: 6,897
Likes: 181
From: Menifee (I.E.) CA
Pro
Joined: Jan 2014
Posts: 575
Likes: 26
From: Sunny Southern California
I was wondering the same thing. But taking a guess it sounds like just swapping out the exhaust from factory to an after market unit. I could be wrong though, as I've been know to be wrong in the past. 
Melting Slicks
Joined: Jul 2008
Posts: 2,151
Likes: 6
From: Oceanside Ca/ Tampa FL
. This is a mod that is done with either the NPP or Bi mod exhaust. The muffler is cut open and the straight pipe that runs through to the inner most exhaust tip (as your looking at the rear of the car) is perforated from the factory. The perforated pipe is then covered by another piece of 3 inch exhaust to act as a housing and welded up. It makes the car louder since the perforations are now covered. This is the C6 muffler mod. Hope this helps, Jay
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Melting Slicks
Joined: May 2007
Posts: 3,269
Likes: 25
From: Simi Valley Ca
Royal Muffler in Chatsworth is one of the best around. They are also the shop that Forgiato uses for all of their exhaust upgrades. When you go to this shop expect to see plenty of exotics. He is always working on high end cars.
http://r1motorsport.com/
http://r1motorsport.com/
Burning Brakes
Joined: Jul 2007
Posts: 870
Likes: 15
From: Upland, CA
Thats where I had my ZR1's opened up and had this done. I had a broken weld on the inside and just decided to open them both up and have them welded so I wouldn't have to worry about it again. He's my go to guy when it comes to exhaust work! Worth the drive to me.
Melting Slicks
Joined: Aug 2006
Posts: 3,123
Likes: 116
From: North Dallas Forty Orange County, Ca.
St. Jude Donor '08-'09-'10-'11-'12-'13, '15,'21