I have the 5.3 Vortec engine in my 99 Chevy Silverado(88K mi) & the "noise" is there at startup. Call it piston slap or lifter noise or whatever, it is the "marbles in a can" noise.
On the GM truck forum, it is attributed to variations in the main rod bearings, rings hitting a carbon buildup in the cylinder or the infamous "piston slap" based on diameter tolerances.
With M1 10W-30, over the colder Wisconsin winter months, the engine was noisy for the 5 seconds at startup & than again at the 1st acceleration after pulling out of the driveway.
I was planning on trying the M1 Truck & SUV 5W-40, but my OCI came up mid-April, before I located a Walmart that stocked the oil. Used Pennzoil 10W-30 HM on shot in the dark & have been very pleased with the results.
I realize this is partially due to the warmer weather, but the engine noise is greatly reduced with Pennzoil HM, which is a thick 10W-30.
I don't know if this is connected to a filter DBV issue, but it almost seems like the M1 10W-30 synthetic drains more out of the engine than other oils.