After seeing Tester’s reply, I did some searching and reading on this.
The best I can tell is Nissan’s QR25DE and VQ35DE engines, between 2002-2005, had their variable valve timing set to include EGR functionality. This momentary “pulling in” of some of the exhaust gas worked fine if the pre-cats were in good condition.
However, if anything ever caused the pre-cats to begin to fail, the substrate powder would get sucked back into the combustion chambers, resulting in oil burning.
It’s not clear if the oil burning happened because the substrate powder, in combination with the compression rings, grinded away at the cylinder walls, or if that powder plugged up the oil control rings. I would have thought the former, but when I see meisterben’s comments saying the oil consumption began almost immediately, it makes me wonder if the latter could be happening.
Perhaps a compression test would tell.