even a 4g91 turbo will not benefit from E3 ECU without proper tuning. not to say it wont work, it does work rather gud compared to non turbo ECU, its just not efficient.evo3 ecu on a 4g91 is totally useless la... unless urs is 4g91 turbo la....
regarding ur radiator prob... if ur water temp is stable... then just leave it.... if not just go for double layer radiator like those on evo/gsr.... then change ur termostat to those lower temp ones.... these should be sufficient.... to me... aluminium radiator is very much on bling factor.... somemore recent years there hav been so many types/brands of aluminium radiator where u dun even know whether they r really of quality......