Maps are subject to restrictions from the car manufacturer. The engine has to pass strict emmission control across Europe. Therefore the engine can be held back to cover this issue. A tuner can remap the engine, alter parameters so that these restrictions are not so tight. I had it explained to me like this......Imagine that your ECU is like a graphic equalizer. You can alter bands to fine tune what you want to acheive. You also have an upper and lower tolerance band to work in. Apply this to mapping and you've got the same sort of thing.
So in answer to your question, yes!
