An improved engine control system using a NOx sensor is disclosed. The identification of whether a web page has changed after it has been visited by a user is also presented. A first error measure is then calculated by testing for differences between the first image part and the third image part and quantified as a first error measure. The remote device may query the IVR system to identify a call agent, in a call center, whose profile matches the information, obtain contact information of the call agent from the IVR system, and send the contact information to the user device. The stiffener panel is removed from the rib after the assembly operation.