Is there anyway to adjust or calibrate the temperature/mileage computer in these rigs? The computer on my '99 was pretty darn close but this new one is off... . I'm off by 2 degrees on the temp, and I'm off by almost exactally 2 miles per gallon, both of these are to the positive. These are only minor discrepancies, but with a truck built this well that's about all we have to bit... about!