Yet again Darren is spot on, trouble is how do you convince an MOT tester that this is a valid procedure for an emmission test when outwardly there is nothing wrong with the car?, the only exception I can recall is for the old level BL's whereby they failed on an idle test but would pass with a raised idle test, incidentally , how many Foci are running around with old software? what sort of percentage motors are in the car parc and why is VOSA not aware of this?( bet my next test is a 1600 focus with fast idle I can't stabilise) !