What brand o2 snsor did you use? If not OEM Toyota, go back, bend over, and pay the extra money for a real Toyota sensor.

If your computer thinks you are lean, but you are running rich, the o2 sensor is not sending the signal.




<<<WAIT A MINUTE>>> You said it runs fine, then pops the code, and runs crappy, right? Then it pops back to normal for a bit? YOU HAVE A LOOSE WIRE IN THE O2 CIRCUIT! The computer can't see the O2 signal, so it thinks lean, and dumps fuel in the engine. When the wire is just right, it leans back to normal.

Go start the truck, warm it up fully, and slowly move the O2 sensor wire around. If there are any changes in the way it runs, you need to check the wires in the circuit.