The local toyota workshop , or any decent mechanic will be able to do this ..
doesnt need speciality service as its a straight forward job for a reputable mechanic ..
There are no " specific to GT4 " mechanics in melb that i know of , most of us seem to have favorites , but its a case of hunt around for a guy with half a clue sadly .
( its not like nissans or VL turbos where 3 million "workshops" work on them daily )