Best suggestion is to either get high flow cats or put the stock cats back on. It should clear the codes and reduce the hissing a lot...probably to a very faint sound with the high flow cats if at all. All test pipes (ART, resonated, and non-resonated versions) will make the hissing and raspiness very audible to varying degrees.
The test pipes are going to amplify the rasp and hissing that the engine is already prone to making.
Last edited by XLR8SN; 10-03-2012 at 09:57 PM.
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