I'm pretty certain I've got one or more dribbling injectors on my 2007 311 CDI, they're the Bosch Piezo type.. Symptoms are - rough idle when hot (as though it were running on 3.5 cylinders or imagine putting the choke on a hot petrol engine), very smoky at idle, clears when under way after 30 seconds or so and, oil level going up. Before I pull the trigger on £750 for a set of 4 recons, I'd like to try and pin things down to specific cylinder(s) via a leak-off test, I can borrow the kit off a mechanic. Can anyone provide a specific range in ml/min so I can gauge which cylinders are dodgy and possibly confirm my logic in that a dribbling injector will produce a lower leak-off rate than expected whereas a knackered injector will leak-off at a higher rate or doesn't it work like that? I appreciate that normally, if one cylinder differs from the other 3 significantly then it's likely to be the dodgy one but without a specific target range, how would I know I don't have 3 bad and 1 good? Thanks.