Adaptive Equipment problems of the 2005 Chevrolet Colorado

I would like to report a recurring stuck throttle problem I have experienced with my 2005 Chevrolet Colorado LS crew cab z71 4x4 with a 3. 5 liter i5 engine and automatic transmission. On 6/28/06 while slowing and turning into a parking spot, my engine raced to full throttle. I nearly crashed into the car in front of me, but was barely able to apply enough brake pressure while turning off the key. The dealership towed it in, could not find any problems, and blamed the floormats. On 8/28/06, while stopped at a traffic light, I felt my truck lurching and observed the tachometer at about 1300 rpm. I checked to see that my foot and floormats weren't touching the throttle in any way. I shifted into neutral, where the rpms jumped to 3,000, and back to drive where they dropped down to the normal 700 rpm idle speed. I carefully drove to a different dealership. Their paperwork indicates that no engine fault codes were found, the throttle control module was responding properly to commands, and there was a software update available for idle control problems -- which they installed. For the next year and a half, I did not experience any other instances of this problem. Then, on 3/3/08 the engine suddenly raced again while parking. On 3/31/08, I was slowing in a straight line at a traffic light and experienced the throttle racing up on its own. I was able to force the truck to a complete stop, shifted into neutral, and the revs dropped back to normal idle. I am writing to NHTSA to report the problem, inquire if others have experienced similar issues, and ask for direction on my next course of action.