I have a 90 Si hatch with a JDM D15B Vtec with a Rywire OBD1-OBDII harness that came with a p28 that has always had a code 41. I recently got a P08 off Ebay. I am aware of the O2 sensor differences. When I plug in the P08 it will idle fine with no CEL until it hits temp then it will bog down and throw a code 9 for the CYP and idle low and rough and just not run right. Obviously it doesn't throw the code 41 because it's not looking for the heater but the P28 doesn't give me the code 9 and until I can get a known working P28 to try out I'm trying to exhaust all my options. I have tried different O2 sensors, in the car right now is one bought directly from Denso. I have followed all the trouble trees for both the code 9 and 41 and both get me all the way to try a known working ecu and if that fixes it buy one. Is my next real option to chip my P28 and load a P08 map?