I have a 2001 Yukon that I’ve owned for 10 years… it’s going to ****. Replaced ECBM, radiator, deferential, window regulators, and the AC, on and on… It’s got 135K and the 5.3 is a piston slapping DOG. Serious lack of power and always has. I did a cold air intake free flowing exhaust.. Hypertech...