GMC Repair: Engine noise, probabally, million vehicles

Question
I have a noise very similar to a lifter sticking which has gotten louder the last few months.  Only at cold start and lasts until oil circulates for 2-3 minutes.  Appears to be coming from passenger side.  Complained to dealership while under warranty and they advised me that it was no problem.  Now it has become a issue by getting louder, no firing miss.  Vehicle is 2001 5.3.  I have tried different oil weights with no positive results along with detergents.

Answer
Hi
From experience, now, I have run into this I think you MAY be looking at a failed lifter that has eaten grooves into the camshaft.
It is Kinda a problem with these engines. Right (passenger side) I also have noticed seems to be more likely cause for some strange reason.
I say that because you run into it more than anything else making this noise.
Now also remember, GM probabally sold close to a million vehicles with the 5.3L in it that year. So even if 10% have a "problem", well you do the math.
I know that does not make you feel any better.
I would tell you to take it to a good local engine repair shop or mechanic, and have them diagnose it properly.
I can also tell you, it MAY require disassembly to actually end up finding the problem (Removing Intake and then removing Center Valley cover and inspecting lifters/cam).
I hope this helps.
JUST ADVICE frome experience.
Good Luck
Pawl