Who said there was no issue?
I stated there is no common fault here, we don't get multiple owners complaining of this issue. I certainly never had an issue with either my GS300 or my GS430, and nor have the hundreds of owners here.
From what you describe the fly by wire throttle system could be an area for investigation. Whilst no fault codes are generated, by data logging all the sensors you would probably get a good indication of where the fault is occurring, by looking at the data when the issue occurs.