XJ Oil preasure/Leakage

My 93 XJ (4.0 HO) appears to be leaking oil at the oil filter, I changed the oil filter with a K&N and it is still doing it---suggestions please. Also while I am driving along, my oil preasure stays at about 40. When I come to a stop it is below 40 about 1/4-1/2 to 0. I know these two are more than likely related. What should my oil preasure be at on a normal basis and should it move at all. This is not a daily drive but it eventually will be and I need it to be reliable. Thanks so much.

If the leak is definately coming from the oil filter area...and it still leaks after changing the filter it is most likely coming from the oil filter adapter where it bolts to the block...or it could be the oil pressure sender leaking and it is spraying on the filter area...THAT would explain the funky oil pressure readings...clean the area well with engine cleaner and see if you can see exactly where the leak is...

How hard is that adapter to change?