Throttle Position Sensor and Idle Air Control valve. They are both attached to the throttle body with small screws, and are removable on the '05. Based on your problem description, it would seem more likely to be the IAC but both of these can get really gunked-up from all the sludge accumulating in the throttle body, especially an 8 year-old vehicle with 190K. The required standard disclaimer here is that your problem could also be cause by a number of other things as well - misfire has quite a few possible causes. But the throttle body cleaning is something fairly easy to try, and best of all the only cost is a can of TB cleaner.