Just keep in mind that the gryphon programmer is always going to be a little off no matter how accurate the tire size and such are. An easy way to see this is to watch the average economy guage while driving like your racing. From a roll of about 30, floor it until you hit 70. Then let off the gas and watch how fast the average climbs back up until you get back to 30. I've gotten my average to say over 30 by doing that. In reality driving around by flooring it then rolling is not going to improve your economy.
For accurate economy you have to still use the pen and paper when you fill. The average really isn't accurate until about 10 or 20 hours worth of driving.
I'm kinda curious about what your thinking of using the MAF for. With that I think all you can get is the amount of air going in and with some calculations an estimate of fuel going in at a given rpm/% engine load.