I added 23% and was pretty much right on the money, but my gas maps were pretty rich to start with. I also run decapped WRX injectors.
If you run open loop, you can actually get pretty decent mileage on the highway too. I average 27-28mpg. One trick is to keep the maps pretty lean up into lower boost (4-5psi) so it doesn't dump fuel as you go up hills, etc.
A few of the basic settings were (this is for an MR2 turbo/3SGTE, 1998cc):
injector offset- 64.00
cranking- 1.7 (you need to inject about 3x the fuel to get it to start when cold, but it will start)
post fuel- 20, 20, 20, 20, 18, 11, 7, 0
Crank fuel comp- 65, 65, 65, 65, 59, 36, 23, 0
It's probably not anywhere near optimal, but it drives better than the POS toyota ECU ever did. Someday I'm going to drive it to NC and throw bottles of whiskey at JD until he tunes it.. er, fixes my dumbfuckery.