hey guys, i have a 85 impala with a 305, quadrajet, and its all computer controlled

with esc
well i noticed my timing is off because i hear slight pops through the exhaust and it goes away when i jump pins A and B to stop the computer advance.
i bought an aftermarket timing pointer, found TDC and marked it on the new pointer. On the timing tape it shows 0* when the A and B terminals are jumped. and shows 20* when running normally at idle.
my questions are
1) is it normal for the computer to be advancing that much at idle?
2) where do i go from here?
Im very new at this, just bought the car this year so please bear with me

Let me kno if you guys need more info
thanks,
clint