This weekend I got together with the MadMsheen and we installed Alternate Map Switching in my Evo. This enables me to run the car tuned for 21psi, but if I want to run 24psi, all I have to do is flip the switch. This isnt just limited to boost settings. In the spring, when I run meth, my primary tune will be a 24psi pump gas tune, and for the track or when I wanna play on the streets, ill just flip the switch and have a 30psi pump gas + meth tune. You dont even have to pull over because its switch on the fly and takes 1.5 seconds (if that to switch the tunes).
There is also an additional feature to this. You can set it up in your tune for it to switch maps automaticly. Say im running meth and my car detects knock (detonation), the car will automaticly switch to the 24psi pump gas tune until a preset determined amount of load is reached, and then it will go back to my 30psi pump gas + meth tune.
There is really a lot more that this can control and I definately suggest this as something worth looking into