HYUNDAI COUPE JUDDERS

I OWN A HYUNDAI COUPE SE 1999, SINCE DAY ONE IVE HAD PROBLEMS, THE CAR STRUGLES TO START FROM WARM AND JUDDERS SOMETIMES WHEN DRIVING AND CUTS OUT AT LIGHTS, BUT ONLY HAPPENS SOMETIMES, I HAVE CHANGED TPS AND AFL, AND FITTED NEW FUEL FILTER AND HAD THE IDLE VALVE CLEANED, IT HAS MADE NO DIFFERENCE, ANY HELP WOULD BE GREATLY APPRECIATED