2000 Chevy Camaro Voltage Dropping

I'm having a problem and it seems to be primarily when I have the AC on. When I'm slowing down and the car downshifts the voltage, tach and oil pressure almost bottom out. It only does this when I'm going under 30 and coming to a stop and it does it through every gear back to 1st. The RPM's will hit almost 300 and consequently almost stall, the worst is when it does it going into a turn. I believe it could be the voltage regulator however I'd like some feedback before spending any money.

Thanks,
Steve