'98 suburban idle prob

I need some help with a ’98 k 1500 suburban that has an idle problem.

What it does is this, on a hot restart the engine starts then the rpm falls off and it will die, or almost die. On the second restart (if needed) it starts and idles as it should. (this is in park)

Next after driving for a while, when stopped at a light idling in gear, the rpm’s begain to flucuate, at times. (as in kind of a rolling idle)

Anyone have any thoughts as to where I might look for the culpret of my problems.

I have installed a new 5.7 gm engine, banks ehaust with new o2 sensors, k & n air intake system, had the injectors cleaned/rebuilt while engine was out, new plugs, wires, cap & rotor, new fuel pump & filter, had the transmission & transfer case rebuilt with new a convertor, and had 4:10’s installed.

Thanks
Ike

I'd check the idle air control actuator.