Ive been using EMS for quite awhile. My MR2 Runs it and ive just finished a wire up on a rb20det powered ceffy and im about to start on a RB25 powered R32. The setup ive been doing is leaving the stock ecu in to run idle and aircon and so on. and wiring the ems in to ignitor and injectors and so on. Nissan consult will still work on the car. Car is fully tuneable as if it had a full on stand alone ecu. Just easier to setup and the factory ecu powers all the sensors the ems just reads them. All you gotta do is cut the ignition and injector wires from the ecu and run em on the ems.
The EMS stinger is the one ive been using the most. It can do antilag, Nos and a whole list of other functions which can be triggered by RPM, TPS, Boost or a combination of the two. Because the standard ecu is retained we dont have to trigger the fuel pump or anything so you have 4 outputs to play around with.
Im not a tuner i just wire them in. I get one of the guys down Bunbury way George his name is to do all my tuning.
EMS Website
Only thing ive noticed with EMS im not sure if u have to do it with other Aftermarket managment is the locator on the exhaust cam for the cas has to be snapped off and a base timing set of 10 BTDC. Apparently the nissan sensor likes to trigger at 60 BTDC and the ems prefers 10 BTDC. Just what ive heard i dont know for sure. But i know PFC is just plug and play. The choice really comes down to which tuner you wanna go with. Every tuner has their preference and i find if you go with a ecu they prefer youll end up with a better overall package because their not trying to learn a unfamiliar ecu.
Just my 2 cents hope it helps.