2000 yukon 5.3 falls on its face

[Tahoeyukondenali]

90 psi oil pressure -- is that measured with a known good mechanical gauge? Way too high IMHO.

That engine needs to warm up. I don't know if it would help the power, but it would help the efficiency of the engine. Has the radiator ever been changed and, if so, to what mfr and part number? Thermostat? Recommend OE temp and mfr as thermostat quality varies and is generally better with OE.

It's almost 90 lbs only on the factory cluster I haven't put in a sunpro triple gauges but that should be my next move

 

[avalonandl]

Those 2000 5.3 were under powered. I PUT A hyper tech tune in ours helped a lot. Make sure thermostat is correctly operating

 

[mikeseay]

Check or remove your catalytic converters,
“You can’t win a pie eating contest if you have constipation” ….meaning you can’t put more in if you can get the old out.

 

[irwires]

Have you checked the back pressure around the cats? Could be partially blocked but not enough to set a code yet?