To anyone that runs across this thread in the future: Tighten your throttle body bolts!
I did that and the problem has just disappeared. It's been two days now and no issue at all. Now if you will excuse me I am off to apply for my new job as a mechanic at the lousy dealership that couldn't/wouldn't figure that one out.
Guess it's easier to blame aftermarket parts when you have no clue what to do to actually troubleshoot the problem.