Hello,
reviving an old thread, sorry about this 8-/
I own a 2006 euro spec RX400h with a bit more than 255'000 on the clock (that 160'000 miles).
I experienced this yesterday (both "town speed" and "highway speed"), it never occurred before.
I was suspecting the gazoline I put in just before leaving on my trip then found this thread and others on the same subject.
The tank is almost empty so I'll fill it with "better" gas tomorrow and do some tests.
If issue still occurs, do you know how to check if the TSB were properly applied (this car has not seen a Lexus/Toyota shop for two years) and if there's a way of applying them on my own (with Techsteam)?