o2 sensor mV questions

So I finally hooked up my datalogger on my '90 corvette. I found out why in closed loop it is pulling all my fuel making it way too lean I think.

I've been having to leave my car running in open loop having tuned to run it that way all the time because of this running lean issue in closed loop. It actually runs almost ideal in open loop. It idles around 13.5-14.0 AFR and cruises around 14.5 AFR in open loop. however I would like to get my closed loop working properly. My o2 sensor is reading .860 mV. I think stoich is .450mV anything below indicates lean condition and above indicates rich correct?

It is a brand new bosch three wire I converted it to. When I first installed it, it seemed to be running perfect but after a few days it started doing this lean running stuff. Obviously if it's reading .860mV it tells the computer of a false rich condition and pulls fuel until it's running 17.0AFR verified by my AEM UEGO wideband.

Have I somehow fouled my new o2? What would the mV be if it wasn't heating up properly? I'm thinking I may have some bum wiring or lack of power getting to the o2 to heat it up. I have long tube headers and the o2 is located at the collector.

What voltage does it say at key on and before its warmed up should see ecu saying 0.450-0.460 odd

It shows .450.84 cold key on engine not running.