Well I guess I should preface this reply with the fact that I live in Florida and there are no inspections.
I respect those who want "clean air" but considering the quality of our air and the fact that the ROW is as interested in clean air as anyone else, I doub't that anyone but the EPA could quantify the additional pollutants released with and without the SAI system. The ROW does not have the pre-cat cats or the SAI. Probably installed by Porsche because of Kalifornia's emissions requirements...
Please note that I am not removing the system or the cats (yet
) but only changing the settings on the DME to turn off the SAI CEL/codes. I will probably install headers with-out the pre-cat cats, but that is not part of the discussion.
For those with state inspections, I doubt that most could catch the difference once the cats are up to temp, and probably even if the cats were cold. The CEL light won't be lit and no codes are stored. We used to have just the tail-pipe probe testing and a visual (by a blind guy). No way this car would fail the tailpipe sniffer without the pre-cats. I had a turbo Supra that had factory pre-cats on the stock exhaust manifold. Guys routinely replaced the factory exhaust manifold and left the primary cat without any emissions testing problems or other difficulty. Hard to even see on visual because the pre-cats were so hidden.