your car will be slow and you injecotrs and afm will max out it will be laggy as they say.
before you go futher have a read of this
http://www.meggala.com/modys.htm
then have a think
on paper it all sounds great but in reality there are issues lag etc.
this set up would be workable on a stock rb25 but did you want to go down that path there is nothing wrong with makig a mistake most of us do it If you want a bit more grunt fit a vg 30 turbo to your rb 20 and that will happily max your injectors and afm wont cost a fortune $4-600.
with the twin set up 5 grand plus will be needed to make the system work at a reasonable level if the manifold is free try it out but only use the stock boost setting till you get it on a dyno you will be coming close to maxing outyour injecotrs and you will blow your motor.
cheers
meggala