Engine idle and lights

2002 f-250 powerstroke, 90K, 7.3
when at an idle the engine 'pulses', the rpms go up and down and all lights inside and out pulse with the sound of the pulsing rpms. At higher speeds you can not tell if the engine is pulsing or if the rpms are fluctuating however the lights continue to pulse.
It is almost in a 1 second cadence, on-off-on-off.
Have a new fuel and air filter in place, no change. Thinking of moving to the fuel pump next. Any thoughts?