High Oil Pressure 5.3 Vortec

[VITAL277]

I have a 2000 GMC Sierra SLE Z71, 217,000 Miles. The truck sat for about 8 months and yesterday I renewed the tags and changed the oil. The truck had normally ran between 40-45 on the OP Gauge, now it's idling on 45-50 and now at 40mph it's about 60. I don't remember it being this high before. I am running 5w30 in the engine but I'm wondering if the long "Sit" may have caused the oil to sludge up and with the change maybe some of that got in the new filter? Side Note, I'm wondering if the Stepper Motor could be bad as well due to when I shut the engine off it doesn't drop back to 0 on the OP Gauge, about 22, but when I turn the key back on it drops to 0 prior to starting the truck then it's right up to 45-50. Once I'm on the accelerator its up to 60. I haven't driven it out on the highway yet and just looking for some input if anyone might have some??? Should I be concerned? If it is the Stepper Motor, is that a big issue? How would I know if it is not the Sending Unit?

Thanks again!

 

[GitrTruckin]

I have a 2006 model with 70,000 milies, it idles at about 45 oil pressure and at 60 mph is around 55 oil pressure I would say its correct.

 

[VITAL277]

I changed the oil again in case something had got stuck in the oil filter and was causing the issue. Synthetic and Wix filter. Now it's about 50 at idle and 55-65 at 60mph. When I turn it off the truck the gauge never goes back to zero, sometimes it's on 25 others 40. It zeros out when I turn the key on so think it might be the stepper motor in the cluster