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      10-08-2012, 02:03 PM   #9
Vintage
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Drives: 2010 Z4 35i and 2014 535d x
Join Date: Aug 2009
Location: Austin, Texas

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there are two sets of stock cats on the OEM exhaust. one set on the Down Pipes (or DPs as everyone calls them) and another second set midway back. if you buy Eisenmann the whole system is replaced up to the DPs, so you would still have the OEM DP cats minus the mid cats. that is my long way of saying that simply cutting out the mid cats should be a good sound improvement and a little bit of a performance boost too. now do the golf tee modification to hold open the second muffler bypass all the time and you are set!!!