I have a 2007 Chevrolet Silverado 1500 with the 5.3 engine. It appeared to loose power about 92 MPH, but I soon found out there was a factory installed, computer speed governor. I hear that this can be removed by a code change in the computer and that is accomplished by what? Do I need to buy one of the computer diagnosis devices? If so, which one is best, for this task?