Just had my cats and O2 sensors replaced so it could pass smog. On my way home from the smog I got the check engine light. Truck was running fine except at idle it runs rough. P0306 code was present. Checked the plug, it was sooty. I replaced all the plugs. Noticed the plugs on bank 2 were all black and sooty, bank 1 plugs looked normal. Fired it up and same problem, swapped wire and coil with cylinder 4, problem stayed in cylinder 6. Then I got the bank 2 system too lean code and the truck started spitting soot out of the tailpipes. Fuel pump is less than a year old. Changed the MAF sensor and checked for vacuum leaks. Any ideas of what to try next?

 

O2 senser