P0133 code has me burning through O2 sensors

[MyExplorer03v8Lim]

I had my engine replaced a year ago and it was a very quick and dirty job by an untrustworthy shop.

I don't want to blame everything on the shop but a year later and I'm still finding things they didn't bolt back in properly.

For my p0133 code, I know the oxygen sensors are a symptom, not a cause. I just replaced my B1S1 (upstream, passenger side, before the cat) for the third time. Everytime I replace it, the car runs better, gets better fuel economy, then starts to slowly but surely devolve bad to a rough running state.

My thought it maybe a clogged cat. But wouldn't my downstream sensor be throwing codes too?

It has new plugs and some new coils. Haven't touched the injectors. Where should I start looking to track down this code?

Here are some screen shots of the trouble code and freeze frame:
https://imgur.com/a/o38BW

 

[lincolnshibuya]

have you tried swapping the upstream sensors? if that code moves to another bank then it's a sensor issue otherwise I'll check for vacuum leaks and clean the MAF first. What brand of sensor you used?

 

[MyExplorer03v8Lim]

have you tried swapping the upstream sensors? if that code moves to another bank then it's a sensor issue otherwise I'll check for vacuum leaks and clean the MAF first. What brand of sensor you used?

It's been bank 1 sensor 1 three times in a row. The past two times I've replaced both of the upstream sensors with Bosch.

This most recent time, I only replaced the one throwing the code. I didn't buy Bosch, this time I went with Denso (cheapo) because I figure it'll get gunked soon anyway. Well so far so good. I drove 10 hours on it yesterday and my average mpg was 17.1. That's up from 11-11.2.

The MAF is clean, and I filled the intake up with smoke via the brake booster, didn't see anything exiting from anywhere other than the air box. It could be that I'm not good at finding vac leaks though. This was my first time ever trying.

I was thinking maybe an exhaust leak. Thoughts on that?

 

[lincolnshibuya]

it will be easier if you have a scanner that can show you graphs on the sensor output voltage, so that you can compare between banks.

Also the graphs on fuel trims can show you if there's a vacuum leak. Fuel trims go down when the rpms go beyond 800rpm.