97 integra rs

Helping my bro..his mechanic did his swap (mechanic left country)...car came with usdm b18b1 obd2 engine originally (had bad rings)..he swap it to a b18b japanese version obd2 version...technically since both motors are the same? All plugs from harness should be plug in back the same right? We found a plug loose but we dont know were it goes? I took pics of the plug we zip tie for now until we find the destination. TiA
No check engine light and car runs fine. But still we wondering what this plug is and were it goes.

 

What color at the wires on the plug? 94