This is very similar to my symptoms, changed thermostat and now engine temp sitting low. Poor idle, rough sounding, poor acceleration, judder when pulling away.
At the moment I'm looking at cars as the culprit as i thought exactly what is posted here that the timing is out due to wrong engine temp being sent to ECU thus causing rough running, poor acceleration etc.
Would this be the same for z22yh engine?
I would imagine this would screw up the catalytic convertor through timing along with other things.