YOur engine is too new to have a serious problem, BUT the use of regular wax based oils have probably caused you some curable damage here. Your car was MADE to use good synthetic oils, and NOT the junk for quick lube oil change specials. Synthetic oils only need changing once every year, and sometimes longer! You have a dirty IDLE AIR CONTROL VALVE and a dirty THROTTLE body. THese things require cleaning because nasty oil vapors have clogged them up. Many times, actual coke appears and glues things together, like brown glue. AMSOIL Foaming Cleaner and Gum-out will clean these things up. THey regulate fuel mixture and idle speed. If they clog up, the computer misreads engine sensors and the fuel burns oo lean or too rich. Lean fuels wil be a misfire, since there is NOT enough fuel to ffire. HOPEFULLY< you went to a seasoned technician. SOmeone who did NOT use American made spark plugs like Champion or Autolite. CHECK IT OUT. Your engine works best with Denso or NGK iridium pligs, or Denso Twin Tip plugs. Hyundai makes EXCELLENT engines that will last a long time. However, NOTHING will help inappropriate maintenance. It will even discount the GREAT factory warrantee!!