Im having similar issue on 2007 envoy.denali 5.3l. I installed a new mellings high volume pump, with the higher pressure spring as well. Cold it runs beautiful, NEVER any noise regardless of pressure. I checked.pressure with mechanical gauge to.confirm my cluster wasnt bad as i was told the clusters do go bad as well and could generate a false condition so it is important to hook up a mechanical gauge, dont trust the dash gauge, or scanners due to the fact some.may read data from the dash. My performance engine guy and gm tech are suggesting worn cam bearings, while another guy i work with who does.all the engine rebuilding (im a transmission specialist) is suggesting to replace valley plate expeccialy due tonthe fact it is leaking from the rear side. If the gasket is to worn he said it may be leaking to much internally at the seals, at idle 0, stayed 0 while moving prior to oil pump upgrade but now it will increase once rpms are up until it gets even hotter before then it stays at 0 with the rpm increase. If you have afm/dod it may be worth a shot. Another engine guy that does High Performance Engine also suggested a different melling's pump that could possibly patch the problem he said it runs about 75 PSI cold and I would probably still hold 20 to 30 hot but I really do not want to change the oil pump again as it is incredibly difficult while keeping the oil pan on I did it once already and I do not want to do it again the 4 x 4 version is very labor-intensive to drop the pan on my Envoy I am going to try a new Valley plate and see what happens
