^^^ This
The PFC is the best bang for buck.
On a stock EJ a PFC will give you all the tune-ability you want whilst retaining all of factory
ECU's functions.
The only thing you'll need to work out is how to switch the Water to Air system waterpump from low speed to High speed when on boost...... The PFC won't do this
afaik.
Actually....... You have a WRX
ecu in it now - How are you switching the speed of the pump for the cooler??