you do need a ECU restrictor unit - your local Suzuki dealer should be able to advise if you actually need a part number
Road & Race advised they cost (new) £250 - suzuki use to do them for free with new bikes but apparently not any more.. (price checked for my sister last week)
i'm not sure what the procedure would be if you had to purchase one privately as you would still need a certificate stating its restricted (had my insurance cancelled when i first started riding as the dealership took their sweet time sending me the certificate
)
hopefully someone who can shed more light will come along shortly