Car Accelerates On Its Own problems of the 2001 Nissan Maxima

I bought a 2001 Nissan Maxima brand new in June 2001. One day while driving in 2004 I experienced sudden acceleration and the engine racing. It did stop after a few seconds but I took it immediately to my neighborhood car mechanic. He couldn't duplicate the problem but found a defective air pollution part and replaced it. The next day, while waiting to take a left turn at an intersection, the engine suddenly raced again and with me practically standing on the brake we slid across the intersection headed towards oncoming traffic. Luckily people slowed enough for me to slide across the intersection with rubber burning, engine whining, etc. A few seconds later it stopped. I was only about a mile from the dealer that I had purchased it from so I immediately drove there and pulled into the service dept. Area. I explained the problem and they told me that they couldn't look at it today but come back tommorrow. I said that I wasn't about to keep driving it with this problem and they said that I could park it in their lot and they will look at it tommorrow. I said "you can park it in your lot, I'm not driving it. " the next day they called and said it must be something with the onboard computer and they would have to change it, cost $1100 not under warranty. What could I do? so of course I did it and complained but it appears to have fixed it since it hasn't happened again. I still own it.