I would initially be checking the quality and accuracy of sensor inputs and the checking the quality of the lambda sensor and ECU earths on the vehicle.
Originally Posted by
James @ M Developments
it will to a point, but air leaks will effect map sensor readings, which can richen things up,
and you can get air leaks on the exhaust side which make the lambda sensor read incorrectly
its totally dependant on the idle strategy as to how effective closed loop is at idle,which again relates to engine spec
This is correct. The chip has closed loop compensation settings that vary from cal to cal so where as one chip may allow a 25% compensation, another may only allow 5%. The ability to compensate also depends on the injector duty on teh load site above the correct one as the air leak will move the speed density map up a load site.