This was done on a 96 WS6. I've been to the site before, but I think this is fairly new. The guy used a homemade manometer to test the exhaust gas pressure before the catalytic converter.
http://www.ws6.com/mano2.htm
Stock Exhaust: 7.5in Hg
Borla: 3.5in Hg
http://www.ws6.com/mano2.htm
Stock Exhaust: 7.5in Hg
Borla: 3.5in Hg
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