depends what you want. if your looking to modify it a lot and get maximum power or just wanting to keep it relatively standard and just get a map..
if you want just a map then...
full service (unless its just been done less than 5k ago. check all sensors and make sure its running spot on, stick a fault code reader on to make sure theres no faults, proberbly a uprated dv anyway cause don't think the standard ones can hold much pressure...
if your wanting to mod and get max power
the above & fmic, uprated boost hoses, uprated dv, full exhaust system including down pipe, induction kit/panel filter... then if you were wanting to go further injectors, hybrid/big turbo etc..
aslong as you have it running sweet when it goes in im sure you will come out with a huge grin on your face...