To change the timing you would need a strobe light preferably. If you cant get your hands on one then play around with the dizzy until the timing improves (i.e. unbolt it slightly and move it until the car runs ok)
To change the idle you would need to adjust the screw on the throttle cable i think on the ga16 tb. By adjusting the screw you will set the idle to the required setting.
Finally you MUST remove the ga16 injectors as the are not neeeded and the car will overfuel. A cg13 running ga16 bits will make the car slightly overfuel.
Mike