I first experienced this very same issue earlier this year, my Lexus mechanic advised this is a known problem and gave me a 250ml bottle of Lexus Injector Cleaner. The problem is now resolved and I have not noticed this issue since. He advised to add this every 3 months prior to filling up petrol. I suspect pouring Shell VPower or any high RON fuel and a heavy foot will also do the trick. Thats just my thought anyways. Hope this helps.
This is what the bottle says:
Part No. 08813-00840
"The LEXUS Genuine Injector Cleaner is a gasoline fuel additive formulated specifically for all LEXUS petroleum engines. It removes injector deposits and combustion chamber deposits, improving rough idle, hesitation and driveability"
