Sorry I am late to the thread, but your very first post and description sounds exactly like what happened to me when my Yukon stranded me in Miami on a business trip. Sitting at a light, truck died. Started it up and it ran fine to get to the customer site. Finished work for the day and drove back to the hotel and it started not running right. No power, then gobs of power. then all was fine again. Started fine the next day, got into customer with no problem. Went out for lunch, sitting at a light, started sputtering and went into limp mode and was shaking and sputtering just trying to get to 15mph. Pulled into a gas station and had it towed to a local GMC cadillac dealership. I may not get this completely right, but I know they told me the motor mounts were shot, and it was rubbing up against some wiring and wore through one of the harnesses. I "think" it was something to do with the AFM wiring, but I can't remember. This was a year ago. They fixed the exposed wiring and replaced the motor mounts and have not had a problem since. I will look for that receipt to see if i can find exactly what they called everything. But I know for a fact it was motor mounts shot which caused rubbing through of a wiring harness. All of these other things you are listing above do not seem to me would happen "instantly" for lack of a better word. What is happening to you seems like an electrical issue like mine. I would think a mechanical engine problem would continue to get worse day by day, not just throw codes and go into limp mode. Just my opinion of course. lol
Edited to add, now that I think about it, I think it was a throttle body cable/wiring. I will look for receipt.
