2001 Dodge Intrepid 2001 Dodge Intrepid

Hi guys,
So I have the infamous 2001 dodge intrepid, 2.7L engine. I have the issue of the engine oil pressure light coming on when the car is hot, in stop and go. I started to diagnosis the problem, installing a temporary mechanical gauge to the oil pressure. The result is that at cold startup I have 50 psi, idling. Going down the road hot I have anywhere between 30 and 70 psi. Idling hot, I have 5 psi. No knocks, no unusual sounds. Just changed the oil. The only question in my mind is, it oil pump or engine sludge? Should I just replace the pump first? Which should answer the sludge question? Any advice for dealing with sludge this late in the game? Thanks.