possibly bad afm????

i have a 77 280z 4speed. when i start it cold, it idles real low(round 400-500rpms) and under very light throttle, sputters a bit. but after it warms, runs good and idles steady at 700-800. now i thought that with FI, it would automatically compensate for the fresh start? it really seems to be running on carbs without a choke! or maybe it's that cold start or thermotime switch i keep hearing about. never have even looked at where those things are on the motor.