Some guys have gutted the secondary cat. Not much power to be gained but its free if you do it yourself or very cheap if a shop does it. Gutting the secondary cat has no effect on you passing smog, readiness, or leaving a bad smell (once the primaries are warmed up) as there is no sensor behind it unlike the primary cat.
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2009 e92 M3 - AW DCT - Apex Arc8s - Corsa
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