My GS300 has developed a strange problem. Drives perfectly until it has run for around 30 mins. Then the throttle response becomes almost non-existent. You need to virtually floor the throttle before the car reacts, at which point it is like kick down and the car leaps forward. The car still continues on it's way and the engine feels fine but it makes for a very weird driving experience.
Interestingly if you flick the gearbox into manual mode the throttle response is completely normal as you move up and down the gears. If the car is stopped and switched off then re-started the throttle seams back to normal and it will run like this for around 30 mins again?

 

I would drop it by your local dealership for diagnosis.... This is probably the weirdest problem I've ever heard, and my years here and owning my GS, I've never heard or run into that problem at all.

GL! If you do decide to find out what it is, def report back to us so we know too!

 

Some have reported issues with the transmission ecu's maybe that is your problem, but its best to take it to the dealer and have them go through it.

Also when was the last time you cleaned out the throttle body? If not recently its just 4 bolts and you remove it that will allow you to fully clean it