I'm am new to prom tuning and have a custom chip in my car for my engine combination. Soon I want to buy my own equipment to to tune on my own as I have a good understanding of tuning carbs. My question is can i change my idle currently without messing with the prom for the time being to adjust my idle. It's 850 rpm in drive and 950 in park which is too high i think for the car (lpe 219). Any help is appreciated. Thanks

Probably not if the ECM is actually commanding that high of an idle. Closing the throttle via the min air screw will just cause the ECM to command more IAC airflow. You will need to change the chip.