If you have the torque app, the O2 sensors and fuel trims will help a lot.
Here's two screenshots of one page I have to monitor fuel trims and O2 sensors. Granted, my converter is original and is starting to show its age, but works ok.
This is at idle, the left graph is the upstream O2 sensor and it's not needing to respond as fast.
This is at 60 MPH, give or take 1-2 MPH, but the upstream O2 sensor is much more active.
What happens is the sensor gets lazy over time and if you have a slow responding sensor like the 1st pic when at cruise you could possibly get some codes.