rcz n18 misfiring problem

Hello everyone, my car is N18 RCZ 200 hp and the fuel meter was constantly giving a malfunction. When I slowed down on bumps etc. the car was accelerating up to 1.5 rpm by itself. Then I changed the fuel meter but the car is stuttering very much when it is cold. The engine shakes a lot. When it warms up there is no problem. Does anyone know the reason or has anyone experienced this before? If anyone can help, I would be very grateful.

If you were able to solve the problem, could you please provide information about how it happened and your diagnosis?