New day, new issue with the heep

Ok so I just got my A/C to work so now the engine has a new problem. I few days ago I noticed that the oil pressure was reading really high for some reason. It has always been normal before in all the years I have owned it until now. At idle it reads 50psi and if I rev the engine or drive it it goes up to 80psi. It goes back to 50 if I stop for a light or something like that. I thought weird but OK maybe the gauge is just messed up or something. Today it started making a loud tapping noise when ever it's idling. If I rev up the engine it goes away till I let off then it starts up again. I hear it more clearly from underneath it's definitely not coming from front of the engine. I talked to some people in my local club and they said change the oil (it was just changed by me a month or so ago) and see if there's any metal in it. Maybe I got a bad filter or something like that so I said what the hell fresh oil can't hurt anything right? I was also told to check the flywheel bolts while I was under there, they are all tight. The oil was full and not very dirty when I drained it out and there was not metal of any sort in the bottom of the drain when I emptied out. It's 2000 XJ 4.0 automatic with 162,000 miles. I have always changed everything on time and it has run fine up to this point. So my question is what do you think could be causing this, high oil pressure reading and loud knock/tapping at idle?

Just from the two symptoms you mentioned I would guess that you have a plugged oil galley. The high oil pressure is a result of the stoppage and the noise is a result of oil starvation in that area. See if you can isolate where the knocking is coming from and look at the oil galleys that feed that area. You can try a flush but I don't know if at this stage if that is a good idea. If it is oil starvation causing the noise then the more you run the engine the more damage is done.

Replaced the oil pressure switch and the oil pressure is back to normal but I still have the noise. It only does it at idle if I raise the rpm's even a little it goes away. What do you think is causing this? Low oil pressure/volume at idle or just a lifter that isn't holding pressure?