97 gsr, originally obd2 with p72. I bought the obd1 conversion harness and am now running a p28 with a crome base map. Now im curious... Does the second o2 sensor get used? If i recall, most obd1 cars use 1 o2 sensor (pre cat) where the one im curious about is the post cat or in cat o2 sensor. Heres a pic if it helps...

As you can see, i have a straight pipe on there right now and am redoing my exhaust. Im hoping i can run open header for like 2 days without that o2 hooked up OR just disconnecting it! lemme know peeps!

 

OBD 1 p28 should only run 1 O2 sensor