Red or Focusboy would be the ones to confirm/deny mpg, and they probably don't drive in a manner to try and eek it all out. I wouldn't expect a substantial decrease if you continued to drive normal, but that's a bit difficult when your car is suddenly more fun to drive.
30 hp/lb ft is roughly a 20+% increase over stock, so it would be quite noticeable. Driveability isn't how much tq you have as much as where it is in your powerband. More tq earlier is better for a dd, later is better for RACECAR.
Go through the dyno chart thread, they all have links to the discussions about the mods and are quite informative.