New charging problem

The Dart has mysteriously started charging at 14v at idle and will climb to 16v when I rev the motor up to even just 1500rpms.

I guessed it was a voltage regulator. I had two more spares, and they did the same thing. Just to make sure, I went out and bought yet another one, and it did the same thing.

This all started right after I installed my new stereo system, but during all of this testing my stereo has been off, along with the amplifier. With the regulator disconnected I am only pushing 11.6v constant. I had the alternator tested at the parts store and it passed.

I am using the new style electronic Mopar black regulator, and the alternator is a 100amp rebuilt. I altered the charging system a few years ago so the sense wire for the regulator read direct battery voltage (same point at which the charging wire (4 awg) returned to battery from alternator.

I really am not sure what to do at this point. I think my alternotr capacity will not be enough for the car, and that going to to a Powermaster 140amp would be a good idea, plus they are internally regulated.

Currently my power draw includes:

20 amps for electric fans (when on)
60 amp potential for radio amplifier (never really turned it up)
7 amps for electric fuel pump
..plus everything else on the car.

Any ideas?

Also, who has run the 140 Powermaster, and what kind of modifications are they talking about when they say "slight bracket modifications" necessary?