98 Chevy Intermittant Charging

1998 Chevy Blazer. It charges intermittantly as I am driving. As soon as any RPM's are increased (driving or at idle) the volts go down. When I let off the gas the volts go back to normal. The alternator was removed and tested. It tested fine. It was put back on the veh and it still does the same thing. Anyone have any suggestions as to what could be wrong?

Found the problem. It was an alternator after all.