Mostly a rant, but I'm open to y'alls opinions/suggestions.

This is a long outstanding problem of mine. Have a fast 90 and inconsistant AFR's between banks. Running a dual wideband setup, left and right bank in the primary O2 locations. I'm 99.999999999999999999999999999% sure this is a hardware problem. To date, here's what I've tried:

Swapped injectors from bank to bank, no change

Replaced injectors, no change

Swapped injectors again, no change

Found two exhuast leaks, fixed them, no change

Tightened intake manifold, no change

Double checked vacuum lines, no problems here

Found crack in #7 runner, JB weld, no change

Crack on #7 turned into broken chunk, replaced lower shell, made new gasket, slight improvement. From here, the left bank would run 2 points higher under 2k RPM. Above 2k RPM, both banks tracked within 0.5 AFR

Remade gasket, Right bank now running leaner than left

Tightened right side of manifold, right bank = commanded, left is off by 1 - 1.5 AFR

Tightened left side manifold, shit hits fan, both banks lean, left ~ 15.5:1, right, ~ 20:1

I'm not sure what's left to try.