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      01-27-2013, 06:20 PM   #4
rockd
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Drives: '11 Z4 35i M-Sport 6MT
Join Date: Apr 2009
Location: San Francisco

iTrader: (11)

The stock exhaust system comes with two pairs of catalytic converters and one pair of resonators. The Sosi X-Pipe removes the second pair of catalytic converters and the resonators.

How much more volume are you looking for (percentage-wise)? Just removing the secondary cats might not get you there...
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