My first question to the dealer. "If its a knock code and the sensors fine whats causing it? Engine coded are thrown for 2 reasons a bad sensor or a sensor detects a problem that is try to compensate for to not damaged the vehicle." Simple as that. So if there is not problem...I doubt there is, they better change the GD sensor.

Secondly, How would a colder t-stat cause detonation? detonation is caused by too high cylinder preasure or temperature or too much timing. A colder t-stat would help.

BTW how would bigger tires affect boost level?? Thats unbelievable I can see it now "Well sir you tire size changes the gear ratio so that basiclly translates through the entire PT and in turn turns the blower slower" Are they serious?!? Tell them to pull there heads out of there asses and fix your truck and then to go learn more about how different components on a vehicle relate or don't.