O2s lean on bank 1 and rich on bank 2

[Boostedforlife]

Rebuilt l31 with mild cam and long tube headers. 2156 os with the l31 tune in it.

Bank 1 is like - 25to30 and bank 2 is + 20-25. New Bank 2 o2 sensor. I was thinking I switched the bank sides but when I unplugged the driver side it shows .445 volts on sensor 1. So I think they are right.
When the stfts are disabled with sensor 1 unplugged it runs great but with the stfts working runs like crap.
Any ideas on how to track down the problem?

[gmtech825]

whats the injector setup on it. I have seen this on engines that had the bank1 and bank2 injectors/wiring reversed.

[Phoenix]

I saw this happen on a C5 where the O2 sensor wiring got swapped after an engine swap. Swapped sides on the connectors and all was well. Also when an O2 sensor is unplugged it will show around .445 volts.

[Cincinnatus]

Check plugs, see if you have a leaking injector. Sometimes new O2s are liars, swap O2s and see if problem follows sensors.

[vlad01]

On my nephew's VS the new NGK o2s were both duds, ecu still kept complaining of lean afrs and plugs and exhaust were sooty even when both 02s were replaced. Economy was 13L/100.

Everything else was ruled out and his mechanic replaced the the 2nd time and this time it fixed the issue.