Several symptoms relate to possible injector problems.
Injectors can suffer from a drop in opening pressure.
This usually occurs after several thousand miles or hours in use. A drop of 200- 300 psi is normal and usually does not have a noticeable affect on the performance of the engine. If a pressure drop is more than 300 psi the injector should be reset to manufacturers spec. A second problem injectors develop is poor fuel atomization. The main purpose of a nozzle holder assembly is to break the diesel fuel into small enough particles that it will burn properly.