what supercuda says is true, you should be looking at wiring issues between the battery and the vr.

it passes through the bulkhead from the battery to the amp meter, to the ignition and then back out the bulkhead again.

Also be sure you are using the same reference for ground, as that can change your readings too.
in case that doesn't make sense, if you are checking the vr, don't use the battery as ground. use the bolt holding it on the firewall as ground, unless you added a ground strap.

or voltage at the alt, field wire, use the alt case as the ground for that voltage.

In theory this should not change the reading. in practice bad grounds will cause different voltages, especially at the vr.

But that is nearly a 1 volt drop, which will screw with your charging system.