Some evc/ebc's allow you to set the scramble to whatever you want. You can take it out, or you can have it set. You can set it for eg an extra 4 psi for 10 seconds. What it means is that if your hitting the throttle hard, your motor will get an extra 4 psi of boost for 10 seconds.
As the above posts state, you have to be sure your car can take the extra. It could run lean, over boost etc
It's not a wank factor, but you'll not really see the extra power to often, it gets 'lost' in your normal boost power, 10 or 20 seconds is not a big time, so by the time you get it happening, your normal boost settings are only a few heartbeats away. One place that the scramble boost is a bitch is on wet days, the last thing you want is more power, and if you bag up in the wet, the scramble boost will cut in and make it worse.
Well thats my bent on it.