We run dianostics on all types of engines to find where the problem is.  On this ford that we have pictured, we checked the electrical dianostics for the injectors on this power stoke.  After, we ran a cyclinder contribution test, which tells us which cylinders are proforming well.  We found the number four cylinders not contributing due to "Power cylinder, valve train or injector problem".  We changed the injector which solved the problem.