After I get it "fixed" by the stealership, they claim that the CEL will reappear since I don't have the stock cats. This is the last Infiniti that I will buy, as this is the only dealer on my island.

Pretty sure they changed functional O2 sensors just to do some labor and get payed, then reset the CEL.

 

What Did Tony say Alfredo?

 

He said it was not the cats and that they were going to blame it on them to avoid coverage. There really is nothing that Tony or I could do to get warranty coverage, but the cats are not what caused the problem.
I have spoken to different mechanics and muffler shops in my area and they all had said the same thing.

Tony also suggested to get my tune checked, which is more probably the cause of the code.

The only thing I can do is get a lawyer, since the dealer's written statement was: "exhaust system was verified and modified cats were found". Basically denying coverage just on the presence of an aftermarket part, which is illegal according to the Magnuson-Moss Act.