Turbo L99 O2 Sensor issue

Currently fired up a customers 13? Camaro SS
Sbe L99
Cam
Converter
Single 78/75 turbo
Injector
BAP

Upon initial start up, bank1 sensor1 o2 is not switching or seeing voltage fluctuation between 60-100 while bank2 sensor1 switches fine between 100-900

No codes present.

With moderate throttle sensor1 will see more for a second or two but then will drop back to 60-100.

I even replaced the sensor itself, as well as removed the extension harness previously installed when the vehicle had long tube headers.

I did not log the vehicle before the turbo build to see if this issue was present before hand.

Trying to get this thing tuned but my bank1 fuel trims are ridiculous because of this o2 issue (30+%)

Any ideas or experience is greatly appreciated.

Thanks,
-Spencer

Is the O2 sensor located in the stock location on bank 1? Or is it equipped with an aftermarket header on that side?
Is there an exhaust leak on that bank? Or a misfire on that bank? Either of those things could cause an O2 sensor that reads low.