Collapsed lifter that un-collapsed? L83/5.3L

[pronstar]

Tried to remote-start our 2018 Suburban today, it made a chirp sound like a slipping belt, but didn't really turn over.

Put the key in, and it ran like garbage - definitely collapsed lifter noises. Got a "reduced engine power" message, and a CEL. Put it in drive and moved the truck, then shut it off. It was barely driveable at walking speeds.

10 mins later, I start it up and its running perfectly. Still had a CEL, codes showed:
P2101 Throttle control actuator motor circuit range/performance
P279C Transfer case Gear Neutral Incorrect Ratio

This truck's transfer case lacks Low Range and Neutral, so one code doesn't even make sense. And the throttle actuator doesn't make sense to me, either.

I cleared the codes, drive around the block and they're still showing up but no CEL yet.

Since this is the Mom Mobile, I'm going to do a full hardware delete. I've budgeted for this on both of my L83 trucks, and I've lost trust in this motor. May as well upgrade the cam since its gotta go anyways.

I have two questions for y'all:
1. have you ever heard of a collapsed lifter that un-collapsed itself?
2. Tuner recos in DFW? I will be installing a mild Stage 1 or 2 cam, and I'd like to retain VVT. I've spoken to a few local tuners and they all want to disable VVT. I'm not necessarily opposed to online tuning, and I've got HP Tuners on this truck and know my way around it, but I've only ever touched the tranny (6L80) tune.

Thanks guys,
Robert

[2xLS1]

There are videos on YouTube where people take the rocker arm and push rod off and stick a long rod down the push rod hole and whack them with a hammer to unstick them so I guess they can be unstuck.

[Pitbull]

I had one that would clack, I'd let the truck warm up a minute and then give the rev limiter a kiss or two... Pumped right up. Now..... Would I advise that? Of course not, but would I do it again? Of course I would...