Im no expert at all, but i will comment because at my last dyno session, oil psi was played with to get more power. If you look at the pull, the psi has only dropped not even a full 4 lbs from start to finish, It sould be a lot of things, Oil return, slight aeration begining, etc . In my opinion i would say its not anything to worry about at all, As pointed out by Al its got plenty of pressure . For what its worth, my engine at 8000 had less pressure that yours, it is a wedge with oil lines returning to the pan and it has a vacum pump. But as i pointed out, they LOWERED my oil psi looking for power.