Aparently the 440cc injectors fit straight into the 1jzgte engine to replace the 370cc stock injectors. Do i need to have an after market computer to get any benifit in changing these over or can the car just be tuned? or is it not worth doing?

the 440cc injectors are a great upgrade for the 1jz... you don't need to buy an aftermarket ecu.. just wind up that boost hehe... but make sure your fuel pump can deliver this boost first ;)
you may find it necessary to get an aftermarket fpr as well....
you could use a 2jz map sensor to regulate the larger injectors i would think without too much worry... i think the 2j map sensor puts out the same voltage as the 1j...

sorry for my ignorance but what is an fpr? :blink:

i've boosted my car to around 14psi on occasion. I'd still not be able to go much past that because of the fuel cut. will i notice a difference with the bigger injectors at this boost?

fpr = fuel pressure regulator :)
to get past 14.7 you need to either get an aftermarket ecu or get a fuel cut defender (fcd)
if you install a fcd make sure you get the fpr and bigger injectors in there and some sort of fuel controller to help you tune it... wack her on a dyno ;)
you won't really notice a difference with the bigger injectors at that boost but as you start raising it you will not need to upgrade as you already have hehe

happy modding ;)

what type of boost could i expect sneak it up to without blowing it to pieces?

well i think realistically with a fpr, fcd, bigger fuel pump larger injectors bout 18psi but i would watch out for those turbos hehe... they have ceramic wheels and have a habit of dying
also you may want to look at getting your fuel rail modified so it is fed from both ends and exits out the center... that way you will 99% not have any detonation problems
if you want to miss all of those bits you can just up the boost right to 14psi as your ecu can deliver this and just buy a fcd to get rid of fuel cut... altho beware of spiking issues or anything that may cause boost to go above 14psi