if you gonna boost it, do a proper job there's so much to think about
there so much other stuff you will need to do once running boost just to get the car running at it's best
if you want to a better 0-60 time on a NA set up I would do these mods IMO
light weight flywheel: this will help the car rev easier
change the final drive of the car. TRD do a 4.5 final drive kit that will be fine on an auto
I think some of the earlier altezza's had a final drive of 4.1, and I think some of the later models had a 4.3 final drive
you can do mods to the air intake system ie : performance panel filter or induction kit
IMO the increase you will get will be about the same with both, but your car will raw with an induction kit

you can also look at sorting your exhaust system out, performance manifold, decat mid section and after market back box
then some sort of management system could be a stand alone ecu or get a Camcon fitted these will all help with your 0-60 time