I had the same exact issue with my 2003 GS 430, the car just stopped accelerating, Engine, VSC and VSC OFF lights came on, the car just would not go above 50 miles per hour. It felt like something was wrong with the gas pedal, I shut the car off, let it cool off for a while and then everything went back to normal, but in the morning it happened again. I brought the car to the dealer and they had to replace a unit that "tells" the angle of the gas pedal.
Good luck.