My oil pressure and voltage meter gauges are moving exactly the same together up and down while idling pretty sure my oil pressure used to stay right at or above 40pounds at idle but now stays below 40 at first I thought maybe my oil pump was going out

-ALSO whenever I am driving if I turn anything on or off radio, cruise control, lights ect. My oil pressure and voltage meter will move a bit exactly in sync in the same direction and same amount. Really have never seen anything like this any ideas welcome

2000 GMC 2500 Vortech 6.0L 190,00miles