Not with 98 heads you cant.
So he has stock grey 370/380 injectors, side feed spec.
You could just put the bottom end in and leave everything else as it is for now
Marc, not an issue, but you already have a 34 so make use of it.
Depends how much power you are happy with - I only make 245 and was more then happy with it - And I made it on stock injectors like yours. I do think you should go bigger though.
If you dont want to spend huge coin, track down some Sti 440's and find a second hand link
ecu etc - injectors can be had for under 200 bucks and links are the cheapest option - not the greatest
ecu but many cars here run very well with them so they do work.