Sounds like a Diesel!!

I have noticed that I am getting a sound out of the motor that sounds like nocking at start up and continuing for a while even after warm up. I have also noticed that that oil pressure is high and then backs down after it is warmed up, with the exception of a few times. I checked the motor as it ran both cold and hot with a stethescope, and have not found anything that seems bad in the head or the block. Do i need to be worried?
I do not have any smoke burning, and I have not noticed any oil in the coolant.
Are the valves adjustable or hydraulic on the 92 XJ?
What should i look for or is this normal?

Probably just piston slap caused by cylinder and piston skirt wear.

The lifters are hydraulic.

Piston slap probably. I have a 94 that does it also. Easy way to tell with auto tranny is to hold foot on brake and apply LIGHT gas pedal pressure while running. If the noise supsides then it is piston slap. Also pull inspection cover for the tranny and check your flexplate mounting bolts.