So I was just driving on a freeway at about 4000 RPM and once I hit some traffic after exiting the freeway, I noticed my car was idling at somewhere between 1850 and 2000 RPM. I haven't had the car very long, but I do know I have the b21f engine, with the mechanical fuel injection and and it does have an O2 sensor. I have yet to check the O2 sensor, but it is on my to do list. Also, I got a major exhaust leak fixed earlier this afternoon, my exhaust had sheered in half at the middle exhaust hangers. I don't know if that has anything to do with it though.