It would really want to be tuned not just installing a preprogrammed chip. Is there a EPROM chip installed already? If so what engine was it set up for?
I was going to say i can tune the car for you, but i see your in Portugal.
I doubt any decent tuner is going to just send out a chip for you as it not exactly a safe option, and if they did try and make it safe they would have to retard the ignition and up the fueling to cover there arse which is a pointless excercise.