No codes are coming up on the scanner. I'll check the temp sensor tomorrow (just got done replacing the front wheel bearing). I know another little quirk is when the car is in park and you rev the engine up to 2k and let off on the gas...the car will stumble a little when the needle drops down to 700.

I have this problem with my 2003 S60 2.4T. The car starts up fine and idles smooth when the vehicle is cold. Once the vehicle is warmed up, the idle is very rough...but the rpm remains at 700. I've replaced the plugs, coils, MAF, upper engine mount, transmission mount, and throttle body with no luck...