yes if you want to max out the turbo. no if you don't. run it at 8-10psi and you might get away with stock ecu / injectors etc. check af's by a dyno run
you will have more lag than normal but not excessive. i'm sure you can find out when you ppl hit fullboost with a gcg highflow on these forums.
this is what it comes down to imo;
option 1: get another rb25 turbo and limit boost to 10-12psi. all is well $250 ~170rwkw
option 2: get a high flow, injectors, fuel pump, ecu (afm perhaps), clutch maybe and tune. $4000-$5000+ ~260rwkw
option 3: high flow, low boost, stock ecu, stock fueling, and see how long clutch lasts, $2000+ ~210rwkw???
do you have the cash?