I had a similar problem on 99 GS400. The dam gas pedal sensor went bad just after the warranty expired. I advice you to get this fixed, because eventually your car will run in "limp home" mode.
When I first bought the car I had similar problems with the car stalling at or just before a red light. Turns out, the senor that gauges the amount of pressure applied on the gas pedal went bad. Of course, I was out of town when my sensor went completely bad. Apparently, according to my salesperson, the 98-99 gs series had this defect and was recalled internally. I had about 50K miles on my car when it completely went.
From my own painful experience, i would have it checked. My dealer originally misdiagnosed
the problem. They said the same thing that it was the O2 sensor. So, I had that replaced and the car stalled on me again on the NJ Turnpike. It was the gas pedal sensor.
Does the car stall when you are slowing down? Like when you are approaching a red light or a toll.
Just when you give it a tap on the gas pedal.
Hope this helps!
