MKIII P1173 How to fix???

Syptoms I have is werid shifting sometimes, goes away when u turn it off and on again.
and the MIL light that says P1173
 
Downstream fuel trim malfunction (bank 2)
Front sensor aged - rear HO2S adaption too lean/too rich RH bank (NAS and EU-3 only)
 
so what does that mean?
 
O2 sensors replaced twice, all 4.
cleaned the maf sensor
dont know what else to do
now it is shifting crazy
 
 
2003 range rover
code came on at 60k now it is at 70k
 
 
any suggestions