Hyundai Repair: My 95 hyundai excel running rough, fuel pressure regulator, fuel management system

Question
i have a question my hyundai excel is running rough in the mornings especially cold mornings it seems to stall very easy and idles really bad. i have replaced the fuel pressure regulator the fuel injectors the co2 metre and yet the car still run's rough i haev a theory it might be the ecu and that it might need fixing but i need your pro advice. i havent replaced the airintake part but also assume that might need replacing and i also have put a new thermo sensor in the car

Answer
There are many things that could make your car run rough, such as an intake manifold leak, a low idle, or a misfire due to any reason.

I'd recommend, if you can, determining whether the car is misfiring.  If so, we should start typical misfire diagnosis.  

If it's not misfiring, or if you're unable to determine, you should probably take the car to the dealer for diagnosis.  There are two reasons I'm recommending the dealer.  First, a good professional diagnosis is likely to save you money.  There are many parts we can guess that could cause your problem (although the ECU is not high on that list), and you'd likely spend a great deal of money just guessing.  Second, the dealer has a scan tool which will communicate with your fuel management system.  With this, the dealer will be able to check for trouble codes and monitor your ECU's data stream, checking to see whether anything in that stream seems abnormal.