difficult to start and rough initial idle, related to 17585 code?

Hi all,

For the last few months I’ve had a progressive difficult to start issue. The car will crank but won’t start until 12-20 cranks. Has a rough idle for the first 30 seconds to minute then it runs just fine. Lots of smoke and unburnt fuel initially. Definitely more frequent if the engine is “cold” (although I moved to Houston so more like hot ambient but cold relative to running temps). No CEL but I finally got around to scanning it and got 17585 code, “bank 2 lambda correction downstream of catalyst: control limit attained”

For what its worth, I have JHM tune and JHM downpipes with relocated HFCs. Houston requires inspection with emissions, so I probably have to replace the O2 sensors anyway. The car has 93k miles and on original 15 year old O2 sensors so I should just bite the bullet and replace them all. But I wanted to see if it makes sense if having a bad “post cat” O2 sensor (which is really still upstream of the cat b/c of relocated high flow cats) would cause such a problem or should I try something else in the meantime?

Thanks for any insight