Here is what the stock manifold looks like with the integrated cats. You'll need to either buy or fabricate some light eliminators for your 02 sensors if you don't want to have codes. All that the light eliminators consist of are a simple tube that pulls the 02 sensor out of the stream. Also when it comes to gains remember, it doesn't necissarily help if you can breathe out well, if you can't breathe in first! So make sure you are doing things to the front side to compliment the back side.
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