general problems of the 2004 Lexus LX470

I have a 2004 Lexus GX 470 (new) that when the a/c compressor comes on the computer advances the idle approximately 250 rpm. The car is standard with automatic temp control so there is no set on/off cycle for the ac compressor. Sitting at an intersection or moving slowly forward in traffic, the car will suddenly move forward (or reverse if backing) causing the potential for a serious accident. The car has been to the dealer who acknowledges the problem and demonstrated the same condition on other vehicles. They requested help from Lexus and were told that this has not been identified as a serious problem therefore there is nothing to be done.