I have a 03 denali with a lq4 LS 6.0 vortec engine that has 180,000 and low oil pressure 20 lbs on cold start at sending unit and no nocks or ticks anywhere. I put two machanical gauges one at the outlet port of the oil pump outlet on the block and on a oil cooler bypass plate and the oil sending unit on the rear of the block that gives me oil psi readings. I use 5w30. I have low oil pressure when the engine is warmed. The machanical gauge on the outlet port of oil pump reads 8-10 lbs which is 3-5 lbs more than the other two gauges which read the same. I will be removing the bypass plate and replacing the oil cooler lines. I have replaced the pick up tube (PUT) twice. Originally there was a green PUT replaced with black one saw your video did job again with reddish orange oring. Cleaned oil pan and flushed engine with the first PUT change. The oil pan looked go with minimal film not even sludge. Next I put in a new milling m295 pump, no change in psi. Bypassing the cooler gave me 2-3 lbs more and I even tried 5w40 with bestline additive gave me 2-3 lbs more. I didn't plastigauge the bearings when I removed the pan, nor did I replace the timing chain, and didn't look at the front thrust cam plate. Bad move on my part. The only thing I can think of is internal bearing walking or increased bearing tolerances. So perhaps rebuild short block or buy a short block or both. Any insight would be deeply appreciated. Short block? longblock?? Where to buy? Or any other possible direction to look at or try? Also if I'm going to remove the engine I will want to beef up or refresh the transmission m32 4l65e or if you know of a better alternative I do tow a trailer. Once again I respect for time, knowledge, and insight. Keep up the good work on your platforms the really help the broke diy guys. Thanks JohnnyA