rich and lean
 

I have a 2000 Maxima 3.0 that is running lean on the back bank and rich on the front bank ( only at an Idle ) and this is what is strange ,only when the a/c is off. when you turn the ac on and the compressor kicks on the O2 sensors start toggling turn the a/c off the front o2 goes to rich and the rear goes lean what is going on ? any Ideas:

update on Nissan cleaned the injectors and the rich code for the front went away now there is 2 o2 sensor codes no switching
went and road tested up a mountain and found it was lacking in power
check fuel pressure and back pressure on exhaust both ok

now I am thinking the injectors are stopped up any thoughts?

pulled the fuel rail pressurized it and took an injector testor and injected the injectors one at a time hanging in the air watching them
they seem to flow great and good pattern