It doesn't drive any different. At least not in my case, I don't know if there is a difference between an R34 ECU reprogrammed to use the Stagea image and a Stagea ECU. But I took mine out, posted it off to Matt at NIStune, then 4 days later I plugged it back in and drove it again. Absolutely no difference in the way it drove, except I noticed the misfire at ~5000rpm cause by the ECU pulling timing/fuel had gone. It was otherwise exactly the same.
It's a null point now, I'm not using it anymore. Turns out... You didn't want to use my ECU. Fkn thing.