Battery light on /overcharging alternator/ stalls

Hi everyone, new member here. I bought an 03 Galant 3.0 v6 recently from my cousin. My current issue is that it stalls, only runs when on the gas pedal after starting. The battery light is on and I tested the alternator on my obd2 and is charging about 15.6. My question is will the engine run like this from an overcharging condition or should I check elsewhere? Primary resistance checked at .7 ohms and Haynes manual wouldn't give the high tension terminal location so I couldn't check secondary resistance on the coil.

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Also, the alternator I tested was from a salvage yard and I didn't test the original one, since I recently discovered the feature playing with obd2.

I adjusted the screw on the throttle body and now idles fine. The battery light is still on but it's probably due to the slight overcharging issue. All I'm going to do now is throw on a new alternator.