My buddy just bought an '03 Duramax with 79,xxx miles. The heat gauge had been working fine for him for the first few hours he had the truck. He went and bought a PPE Excellerator plugged it in and put in a tune and now his heat gauge goes to the 260 mark. He plugged back in the tuner and it said the truck was at 160 degrees. Do you think the tuner caused this or do ya spose he is having gauge cluster problems like everyone else talks about?