In late December i did a 125 mile trip - on a couple of occasions i felt a couple of slight misfires and a couple of mini surges. As i got home the flashing EML triggered and the fault code 0300 (multiple random misfire) and 0141 (Post cat O2 heater circuit malfunction. So swopped out the O2 sensor.
However am still getting misfires but no surges , more frequently, but still not throwing a code up .
The idle appears normal and no hunting and the misfires seem to only happen under load.
Using my OBD and my rudimentary knowledge of data stream readings - the Short and Long trim seems fine, the 02 sensors OK, and the MAP and IAT seem OK .
So thoughts and suggestions welcome as to most likely cause.