Were there any diagnostic codes stored in the computer that the dealer read?
It almost sounds like a bad coil pack. If one goes really bad, it will make that cylinder cut out, shake, and probably give a blinking SES light and/or reduced power light.
Was the vehicle in any big rain storms just prior to the problem starting?
Getting back to the throttle body, did the dealer remove and try CLEANING the throttle body? This is something most backyard mechanics can do. It also involves disconnecting the battery for about 45 minutes while doing the cleaning to re-set the computer to factory settings.
Always remember: wherever you go, there you are!
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