I'm currently running the MPG increase experiment for the Hypertech III & Airaid install. See my thread
http://elcova.com/groupee/forums?a=tpc&s=2826088551&f=5106011751&m=364100799
At best, I expect maybe a 1 or 1-1/2 mpg increase. That would put me at about 12.8 or 13 mpg. Still better than the 10 mpg you're expecting. But at those prices! Wheeeew. Most of us look at it that if we can afford the H2 we can afford to feed it. And it's worth every penny!!!
P.S. At that rate it will take about 25000 miles to get my upgrade investment back. Sooner for you at your prices.