Gas mileage won't really be affected, it is more your wrist that controls that. I have gotten the same mileage pre and post tuneboy. The speedo reads about 7% slower, so it might save you some fine money to keep it stock.

With tuneboy you can open the secondary throttle plates full time (another power restriction). There also is diagnosistic capabilities. Basically you have full access to all 6 fuel maps, 3 ignition maps, secondary maps, rev limiter, and wheel speed constant. Plus you can reset stepper motor and force adaptions (12 min tune).
More info here
http://www.tuneboy.com.au/
However, if you want a custom fueling map done on a dyno, you may be hard pressed to find someone who uses tuneboy or is willing to learn to use it. This is where PCIII has tuneboy beat, PCIII is more plug and play as far as mapping goes.
Molinoman, sounds like you are getting stir crazy. Are you ready to get out of there already?