I had a similar but not indentical situation, where the car would miss at idle after it had been run for a bit... I had the dealer run diagnostics and came back clean and they sent me home after 3 hours even though they sat in the car and felt the missing at idle and agreed with me...

Turned out to be fouled plug 1 of 12 ... Discovered by my local mechanic with no Star Tech Computer, just a few years of experience..

Weird how the Star Tech Diagnostic computer said the car was fine when it wan't... Or do these service depts. not know this equipment yet ???? Perhaps...