2008 infiniti fx35, 3.5L cat efficiency low bank 1&2 after replacing both cats

2008 Infiniti fx35, 3.5L
A friend contacted me to use my scanner for his car. He told me He took his infiniti to the dealer, they told him he needed new catalytic converters. He replaced both cats with aftermarket cats. When he showed up I scanned his vehicle and found both banks cat efficiency low. P0420,p0430. I spent some time looking at data, my question is, when I look at LT and ST fuel trim, LT stays at 0 even if I do fuel enrichment test or produce vaccuum leak, never any change to long term, even if short term is pegged in either direction for extended periods? Also the sensors A/F upstream and 02 downstream do seem to indicate that the cats are not functioning properly as the rear seem to mimic the front, although this is the first time I have dealt with A/F (upstream) reading voltage between .55v-4.65v. Are these voltages correct for air fuel sensors for infiniti? Actually when I look back at the saved data, the rear 02 sensors seem to be doing all the switching and the A/F sensors seem to hover at about 1.5v unless the throttle is depressed and then it jumps towards 4.5v. Anyway if any of this makes sense to anyone, any info would be appreciated. I will try to attach some screen shots of the data.