05 Suburban Low pressure and now high oil pressure

I was on a road trip and came to a stop and the
display showed low pressure. As i gave it gas it
went off. Long story short I replaced oil pressure
pump, oil pressure sending unit, primed it as
well,pick up tube and o-ring. It never ticks and
purrs like a kitten but problem got worse gauge
would go up pass 20 and alarm always digged
while driving. Drove the truck like this for months
b/c I was out of ideas. Got in it last week expecting
to hear that annoying sound and it was gone. This
week now the gauge goes to 80 psi while driving.
Can anybody tell me what the heck is going on with
this truck if you can't I can sell it to you??????