Lately I've been experiencing what I can only describe as a mini or micro surge. Lemme explain...only when I'm in 'drive' and come to a complete stop with my foot on the brake, it's like the engine wants to surge or jump only a few RPM, literally feels like only 50 RPM. Best as I can show it, itd look like this; d-d-d-d-d-d-d-d-d-d-d-D-D-d-d-d-d-d-d-d-d-d-D-D-d-d-d-d-d-d-d-d-d-d-d-d-d-D-D-d-d-d-d-d-d. If I put it in 'park' it stops. Also, as I roll to the stop, NO surging.

There are a couple of things on what we call the "lopey idle".

There is a reflash for certain year trucks.
If that doesn't cure it and it does it while still hot it may need a new Rail Pressure Control Valve (RPCV). It's mounted on the high pressure fuel pump.

By the way, it's only been doing this very recently...for the last couple of weeks. And I suspect that it started shortly after I started using a fuel additive (Primrose 405). So, if I need the reflash done, does the GM 100,000 mile warranty cover this ? Thanks in advance.

I would expect the warranty to cover the situation. Mine did it for awhile. Pretty much as you describe. The surge was not at regular intervals and was about 50 rpm each time. Ironically, it quit AFTER I started using Primrose. Go figure.

TC