I think they are usually about 55-58kg/hr here but that could be due to the difference in ambient temp between Jim & I!
When they "go" the reading usually drops to low 50s or high 40s (again, readings here) accompanied by a considerable loss of power and no fault code being logged. Possibly if the reading is completely silly like 4kg/hr the ECU recognises that fact and discounts the airflow reading completely just reverting to a default value for fuelling based on engine revs and pedal setting, I don't know but Porny probably will.
Maybe the Rovacon is the problem, can't say I have tried one of those, my experience is only on a T4/IDS because I am spawn of Satan