Oh, I see now...
I've got a rich condition on my project Silverado right now. I did a V6 to V8 swap on a LM7 tune, but the injectors are higher flowrate (engine is an L59 with flex fuel.)
Anyway, I'm pretty sure it's the injectors on my case, just haven't had a chance to change them out. I'm about 10-11% rich on the LTFT, exactly on both banks. Codes are set for both banks being rich, but truck drives just fine. I believe the ECU can adjust up to +/-25% to compensate.
I just went to look and my upstream 02 sensors with my cheap handheld scanner and they still show that sine wave I was mentioning... IIRC, those 02 sensors have a common ground in the harness. I would look at the ground on them. Otherwise looks like they may be bad. But I'm suspicious because they are reading almost indentical to one another...
I hope this helps.