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Old 01-29-2007, 09:24 PM   #11
Plays_With_toys
Scooby Specialist
 
Member#: 82556
Join Date: Mar 2005
Location: Parker, Colorado
Vehicle:
1996 Legacy L wagon

Default

You said 3" on a naturally aspirated car. That's where your torque problem lies. Its just too big of piping for torque. The exhaust gases are expanding too much in that large diameter pipe and are cooling and slowing down. At higher RPM's you don't notice this because the volume of exhaust gas you are pushing through is so much larger.

If your borla's are 2.25" you should stick with roughly that size piping all the way through. At the very least don't get smaller anywhere along the pipe or you'll negate the effects of the increased piping size. However, I wouldn't go larger than 2.5" anywhere in the system, because even at 2.5" you begin losing torque.

Having said that, your car will have less high end power with smaller piping, so you might notice this trade off if you were to switch. Alot of people experience check engine lights as a result of high flow cat's, It is a symptom of the performance exhausts, so make sure that that is not the reason for errors before you start replacing parts.

Happy motoring!
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