Those TPS sensors have a rep for getting "dirty" at the idle position. With it hooked up and you monitoring the data, slowly open and close the sensor, it should sweep smoothly with no jumping around of the data.

Also verify that the throttle is not being mechanically held open by something preventing it from returning to idle.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.