ive learned after postingg a similar question and learning quickly that i was wrong in the approach .
the only worthwile one i know of is the 550cc supra injector swap AFTER you go an aftermarket ECU and raise the power output by a heck of a lot ....
if its a gt4 your dealing with - it will handle 300 HP on stock injectors with good tuning/aftermarket ecu before having to upgrade .. Anything more and you really need to look at bigger ones.
ill be doing the injector upgrade on mine AFTER the turbo gets highflowed - as im aiming closer to the 400 hp mark