general problems of the 1998 Infiniti QX4

On 7 seperate occasions over the past year the car has accellerated suddenly while driver was attempting to brake. The throttling effect has occurred at various speeds between 5 and 50 mph, but always when attempting to brake. The problem has occurred since the first month of ownership. On one occasion I have applied both feet on the brake pedal at full force and the vehicle still accellerated and would not slow down until I knocked it into neutral. I have had 3 different people in the car when the incidents have occurred. The car has been checked by dealer twice and I insisted that the service manager drive the car for a week, but he was unable to duplicate problem and accused me of driver error. I believe very strongly that the problem with the vehicle will cause deaths sooner or later and needs to be addressed. I will not drive the car in any city area for fear I will run someone down in a crosswalk. Any help would be greatly appreciated.

While looking for a parking space and found it, turned into it and the engine began to race. Vehicle accelerated, hitting another automobile that was parked, driving it up on a grass hill. Vechicle did not stop.