It's not recommended, as the handling of the car will be way out of specifications. I don't know how it's regulated in Bulgaria, but where I live (Norway) a spring change has to be approved by the government before the car is allowed to be on the street.
The Stilo with my new Eibach springs went through one hour inspection before I got my license plates back (they weren't physically taken from me or the car, but virtually). Until the new springs were well documented and printed into the new registrationpapers (for the car) the Stilo was actually illegal to drive with - with no valid insurance either. On the springs there are numbers which correponds with the car version (engine, model, body) and if the numbers in the TUV papers don't match the car or springs I wouldn't get the car back.
MW.