I just recently started looking at the logs from an MPi MEMS 2J engine using RoverMEMS.
The lambda sensor is not a Bosch and I have ordered what is supposed to be a Bosch brand, but so was the one I am using.
After the engine warms up and goes into closed loop, the sensor fluctuates high/low for about five minutes. After five minutes, the fluctuation becomes smaller and smaller tending toward high. After awhile it becomes stuck at the high end or with marginal voltage shift.
Anyone else seen this behavior?