After some effort with port problems, its running fine. But the gallons used and mpg are off. I am getting ~ 8 mpg but VMSpc says I am getting 6. It says I used ~ 55 gallons, but when I fill up it only takes 42. Is there something I am missing, or is this an indication of problems with data sent to computer read out?
No Problem with the setup. Your Engine is Over Reporting Fuel Consumed, thus your Calculated MPG is off.. Is your Instantaneous Miles Per Gallon and Rolling Miles Per Gallon reporting correctly?? You can use the Engine Correction settings to bring the Fuel Used back to accurate.. The formula is Actual Divided by Reported, so in your case, 42 / 55 = .76 ( 6 / 8 = .75 ) So put .76 into the Fuel Correction in the Engine Correction Dialog Box..
The 6 to 8 MPG difference seems a pretty drastic difference; there may be many factors contributing. I suggest you also check to see how closely the distance traveled is to actual distance. When comparing the fuel used to the actual fill-up it's important to be sure the coach is sitting at the same level on the two successive fillups.