Hey guys! I have an adjustable Borla cat-back on my Iroc-Z. Mods are: hypertech thermomaster chip, fan switch, 160' thermostat, th-700r4 shift kit, 3.70 gears, and a gutted air box. The car has run a best of 14.3@94mphw/2.0 60ft. This pass was with a OEM new catalytic converter, and the Borla fully closed. When I first got the Borla put on I left it fully open. My catalyst was clogged at the time. With the Borla open the car wouldn't even chirp the 1-2 shift, even with a shift kit, nor would it spin the tires off the line. I am wondering if anyone has the Borla adjustable on their 350TPI if they have I open or closed and what their thoughts are on this. Thanks guys!!!

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1999 Camaro SS LS1 m6 12.6@112mphw/1.9 60ft
1987 Iroc-Z 5.7 TPI best et. 14.3@94mph w/2.0 60ft.
1984 Camaro

 

You make more torque at low rpm through the muffler, but make more high rpm power uncorked. Best way is to use an electric exhaust cutout on the fly and have it RPM activated.

www.empiremotorsports.net

ODB

 

with a gutted cat and the 2" hole plate my car ran a 13.71 with a 1.840 60' so i dont think i am losing any low end torque. i put the open plate in adn it ran a 13.72 with a 1.849 60' then with the closed plate and a hot tranny the car ran a 13.74 with a 1.857 60' so it really doesnt make a differance on my tpi

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91 Z-28 L-98 Black stock 14.20 @ 97

 

I have a Question on how does this sound? im running a high lift 327 motor with headers and no cat, im looking for something different then the normal flowmaster. all i have now is the OEM duel mufflers on my 82 and it sounds loud. but i would like it to be louder, and have that beautifal tone on WOT

 

The car sounds really good. Not as loud as a LT1 or LS1 for some reason. Whe fully closed the exhaust has a deep rumble and gets throaty when WOT.

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1999 Camaro SS LS1 m6 12.6@112mphw/1.9 60ft
1987 Iroc-Z 5.7 TPI best et. 14.3@94mph w/2.0 60ft.
1984 Camaro