Yaris stalling in very hot weather at low rpm

[serendipity]

Our 2008 4sp automatic 1.5l Yaris sedan stalls intermittently or loses power at low rpm in very hot weather (>35C/100F). Car has 150k kms and has been doing it since around 80ks. Car is completely stock.

The most common set of circumstances is after car has a long period of idling or lots of stop/start driving or slowing down after a long period of highway driving. It starts again immediately with no issues. If temperature is less than 35C/100F then doesn't seem to be an issue.

No engine codes have been recorded. Fuel filter in the tank has been replaced recently and resulted in no change. Throttle body has been cleaned. Spark plugs replaced. Car uses E10 fuel.

To my inexperienced mind it seems like it may be a vapour lock although it does not appear to be related to amount of fuel in the tank.

Any help would be much appreciated!