what is wrong with my 2005 optima lx

You need the test procedures for testing the EGR system. Hyundai as a car manufacturer put a lot of free technical information and workshop manuals on line for Hyundai owners. Check out www.hmaservice.com lots of great information. There is a company that independent auto repair shops "buy" their information from that offer a very reasonable service to do it yourselvers. You can get a one week subrcription or year subscription very cheap. The information is year make and model specific repair procedures, service bulletins, component locations, wiring diagrams ect.... great quality information same as the professionals have ,much better than generic workshop manuals from parts stores, much cheaper than the factory manual try http://bit.ly/mitchell_repair_manuals_online and get an online repair manual subscription.