Help!!! Too lean

Do you have an ODB2 scanner? If you did this might be able to slow down the "parts changing" train that you have been on. Likely you could have paid for the scanner with the $$ saved from one round of O2 sensors replaced.

Here's some information on a very affordable ($30) Windows based unit.

ForScan ODB2 scanner w ELM327 USB

Using the ODB2 Mode6 data, WHICH cylinders are misfiring? At what rate?

Graph the front O2 sensors and compare the rate of change between bank 1 and bank 2. Does bank 2 switch lean/rich at all?

If you are still looking for parts to change, then check the bank 2 exhaust manifold. Looks for gasket leaks or cracks.

Also double check the EGR tube for cracks.