i bought a 1991 integra gs with a b16 vtec swap with the obd0 ecu,[im told it is from an xsi integra], the thing i noticed when i was looking for the ecu code is that the guy who did the swap ran a wire for the second o2 sensor to inside the ecu from the header, the ecu says pr3 on it, my question is why was that wire needed to be ran, and also i want to convert to obd1 so what ecu can i get and what all would i need to get and do for the conversion, and how hard is that to do myself, im not a mechanic but i know my way around a car pretty good, any help is appreciated, thanks