Ok, had to replace a bunch of failing items: MAF, throttle body, and clogged catalytic converter where it had been running rich with an erratic idle.

Now I have code P0133 which comes back as a slow response front O2 sensor. As luck would have it, I had a replacement on hand and put it in. Did the 20 time brake pedal stomp and....code/CEL still there.

Looking for ideas? Maybe drive a few times and see if it goes away?

The car certainly runs better now than it did before but I can still feel that lean running hesitation.

 

I don't think the 20 pedal thing clears CELs. Have you tried clearing it via whatever tool you use to read it? That code is pretty specific to the sensor.

If it was running rich, have you checked for vacuum leaks and replaced thr ignition?

 

The engine was running rich because it was a rebuild and breaking in. Ignition was brand new OEM coils. Not running rich now. The cat was definitely done and I could smell it. My device is just a cell phone GPS device that plugs into the OBDII port and reads codes, not clears them.