I'm still bothered by the obviously unstable ECT sensor. 118.6 is why too low. This will affect HOW the PCM alters the AF mixture. As part of the same run it obviously points to a problem if part of the same run.
The only way I know of to positively rule out a blocked cat is to measure the pressure before and after the cat. A basic health check can be done by removing the O2 sensor and measuring the pressure at the O2 bung hole.
Another exhaust health check is the measure the intake manifold vacuum. It will show up as low vacuum at idle. But will have a decreasing unstable vacuum under stable RPM (say 2500 RPM)
In the data dump above note the STFT. The PCM is adding fuel at a large rate. Also note that it's the same on both banks. What we don't know is if this is the problem or a symptom of the problem.
If this were my car I would "record" a running list of:
- RPM's
- MAF
- O2 voltage bank 1 sensor 1 and bank 2 sensor 1.
- STFT bank 1 and bank 2.
- TPS
Drive the car until the problem occurs. This will crate fairly large data set. This is where having good Excel skills will pay off. The key is to graph the data from a common origin point so that trends over time can be seen. IE which happens first? Or is there a build up until the STFT limit is reached?
Specifically I want to know how the O2 sensors are switching just before the problem happens. In fact pay close attention to any sensor that changes right before the STFT go through the roof.