Throttle Control Warning Light On problems of the 1999 Volvo S80

My 1999 Volvo s-80 t-6 suffers from a design flaw associated with the throttle body and engine warning light. The light is on all of the time. Servicing does not clear the light, so I have begun to simply ignore the light. The throttle body has a problem where the engine runs properly for 20,000 then begins to oscillate upand down by 200-300 rmps at idle. This seems minor, but it almost caused a major accident yesterday. When slowing to a stop at a major intersection, the engine slowed to idle and then sped up just as I was about to come to a stop. The higher rpm caused the car to move into the intersection. If another car had been approaching, it would have struck my car. I asked my wife (this is her primary car)if she had experienced the same problem and she said she had several times. I went on the web and found that many Volvo owners are experiencing the same rpm and engine light problems. I do not know if they have had the same near accident I did, but I must assume they have. Have you received other complaints about this problem and has Volvo been notified? I contacted Volvo and they denied any problem. The words on the internet tell me they are mistaken. Some one could get killed by this design flaw.