I have a 54plate doblo cargo 1.3multijet with 124k on the clock...It's returning 48-50mpg no smoke and in general running as it should,

I ran the software Multiecuscan and i noticed the injectors showing

2 with a minus symbol next to the number values and the other 2 with 0. then numbers...so there not all within a certain value or tolerance so would there be an issue with mileage on them?

I have a little diesel knock when pulling away but nothing at present too worrying just trying to see if there prone with 100k plus to go out of tolerance..if they need refurbing i take it they will come back with new codes and require recoding?

Also if they go too far out of tolerance will they put a light on?

many thanks.