go for the w58 if you are not going to run more than 250rwkw. nicer to drive than the r154. if you haven't bought the engine already, you should seriously consider going to
www.otomoto.com.au and clicking on turbos, then "NEW KIT". the jza80 upgrade kit is awesome, . 250rwkw at 12psi, strong off boost too.(twice the power you have now) you could keep costs down by doing the intercooler kit yourself(trade me $500) and buying turbo injectors (430cc) quite commonly available(replace your factory 315cc ones. you wont need to upgrade fuel pump- its perfectly capable of those power levels. the real key in tying it all together would be that adaptronic plug in ECU. put the electrician costs that you would have spent, towards that maybe. just something to consider. you wont need to pull the motor,or feel sad when someone picks up your mint 2JZGE for under $500!