I've never replaced my pre cat o2 sensor, its been bad for as long as i've had the car. I'll put a new one in someday when i remember. but anyways i went ahead and pulled my throttle body off tonight and HOLY SHIT it was soooo gummed up, i couldnt believe how much sludge build up there was. So i got out the carb cleaner and cleaned the TB and IAC until they were spotless and put it back on the car and she idles fine. I cant wait to see how it does tomorrow morning. I took pics too.