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      05-18-2013, 06:12 PM   #5
Hoa
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Drives: BMW
Join Date: May 2010
Location: GA

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Our cars have two catalytic converter. The main one is on the down pipe. The main one does have sensors. If you get an aftermarket down pipe that has the fittings for the down pipe, it doesn't throw a code. The secondary catalytic converter doesn't have sensors and won't cause any code to show up.

Removing/replacing either one will cause an increase in the exhaust sound. Most doesn't like the combination of removing both if them because it cause the exhaust to sound very raspy.

Removing the secondary catalytic converter will not improve on performance gain as much as the down pipe. Down pipe will allow the turbo to spin more freely and reduce turbo lag and gain some power.