Apparently yes, you can flash a GMC 2006 because if the car is from the United States, on the FAQ page, there is information related to the supported models based on country and year. USA is listed as having year 1996., therefore it's supported, but if you have better knowledge about it, I recommend checking their support page to see exactly what are the supported years, cars, and countries.
Access the following link and go through the available questions. You'll find the much needed information this way.
