td5 injector readings

According to the rave cd injectors should have a reading of +/- 4 when read with a diagnostic tool (in my case its a hawkeye)
Injectors 1 4 and 5 are within parameters but 2 and 3 are reading +/- up to 7 or 8 and occasionally 9 or 10
Does this mean they are knackered or can I tune them in by setting the camshaft clearances ?

if it makes any difference its a 10p engine

thanks

Dave