the quad throttles from GTiR wont work... if only it were that simple! any oversize throttle body (single) which will work for the SR20's should bolt up pretty easy.
To upgrade throttle body you will want to get a chip or ECU tunable system of some sort.
More benificial to upgrade the AFM as it is the pressure point of the intake system with only a 64mm opening. Throttle is 70mm stock I think.
Again you will need to tune the ECU.
Get a chip/nisstune board for good value upgrade.