I just aquired a 1999 chevrolet suburban, it's oil pressure while driving stays right around 20 and when I stop it drops down to about 10. Last night while driving up a good size hill on the freeway it almost like it lost some power and started to feel funny. Not sure if that had anything to do with the oil pressure or not. What could be causing such oil pressure is it normal?

 

Welcome to the forum. The 5.7L, if that's what you have, calls for 18 psi @ 2000 RPM. Obviously I can't vouch for the accuracy of the oil pressure gauge in your I/P cluster, though.

 

Take it from me, Having 10 psi oil pressure at idle is too low. It might only "call for" 18 psi, but it really needs more. It could be your gauge showing wrong readings but doubt it. It's probably easiest to attach an oil pressure gauge if you want to be sure.
My first guess, being that this happened to me, is things are just getting worn out. Nothing's broken yet, but just getting worn. What my father did to fix the problem, and what I did after him, was just increase the oil viscosity. Normally the truck takes 5w30. So run it 10w40 and see the difference. It'll jump a little. Don't jump to 20w50 yet, it'll probably be too thick and do more harm than good on cold starts.
My estimate is if I get 15 psi or less hot at idle, then something's up.

 

Replace oil sending unit change oil get a clear oil reading top off last quart with lucas change out next 3000 miles repeat at 4500 miles ... Enjoy life.