I have heard that if you do not hook the secondary o2 sensor up it will run like crap, I had a ef with a b16a swap, 1990 si. I tried the same o2 thing just hooking it to one o2 sensor and it ran like crap, I then just ran a new wire to the 2nd o2 sensor and then everything started running very good actually. I highly reccomend hooking up that secondary o2 sensor....The Pr3 ecu seems to really need it, because it senses the exhaust out of 2 ports with each o2 sensor. If you hook it to just one o2 sensor it sees the same thing out of just that one o2 sensor and it things hey both o2 sensors are seeing the same thing, and ti shouldnt be the same all the time and the ecu is trying to compensate for it making it run like crappo..

-Brax