hey dude, I have a set of Nismo 555cc injectors in my GTS4, they are straight fit just plug in and go. Don't worry about some obscure help line, just go to a site sponsor or nengun (where i got mine) and get them cheap and the best quality around.
I've had my 555s for 3 years now and once tuned on a RB20 like you then idle and economy is perfect. Can't go wrong!