OK, a buddy of mine has an 07 4.8L 2wd silverado and installer a Diablo tuner to compensate for a larger tire siz and yet correct speedo readings. He switched back to a factory size tire and tried to pull the settings with his Diablo tuner unsuccessfully. I work at a dealer and told him we could try reprogram his ecm to the latest update and that should get him back to factory specs. He didn't tell me he only used his tuner to change tire size or I would have changed that with a tech 2. I figured he did some kind of engine tune or something. Well after reprogramming the ecm the truck ran great until he drove 20 feet and it died. Idles fine but once you drive drive 15 to 20 feet it just dies. No codes stored any modules. I performed ck. Shaft variation relearn and idle relearn after programming. Anyone have a clue what I should do? Truck ran great before.it seems to idle a little lower now. Should I just try and adjust things with the Diablo?