If I don't drive (but my wife does) we can get ~20 mpg average. Now, I get about 16-20 depending on how I feel that day.

Like anything else, YMMV. If you keep your speed down on the hiway, you'll do better. If you lift it, you'll do worse. Any suspension mod, or tire change, will likely result in worse mileage.

Now, I've been doing some reading, and a few calculations. If I'm correct, this induction system should doo better with a different filter piping system. I haven't tested it though.

P.S. I'd like to put on manual hubs, one day. I believe this to be the best thing we can do for better mileage.