Aprilia rs 125 wierd thing?

Hi I have a aprilia rs 125, 2005 and i just got this bike but its very wierd as it says on paper restricted but i had to change my spark plug adn took the old 1 to the garage n they said it was a derestricted spark plug but my bike only goes like 80 mph my mates its at 28bhp and he said he has a restricted spark plug now when i went on his to mine his aceleration n top end were faster than my bike some 1 has messed around with the ecu aswell as they have cut the back of it and snapped the bridge then filled the part where they cut back in could that be why its on a derestriced spark plug as i know 100% it isent fully derestricted to 33bhp and can some one plz tell me what cylinder parting is in full detail in the exhuast / make it breath better thanks