Any possibility that your voltage regulator is overcharging. That or you alternatore is going bad and your volts are dropping below the amp's tolerences. I think it you go done to 10.5 or so it will cut out. Taking the towers down would produce less draw and so you may be staying afloat at around 11 volts or so. If overcharging, amps will cut out in the 16 v range due to protection cricuitry. Overcharge seems less likely do to the fact that you realize performance when you lessen the load.
I would hook a voltmeter up and seenwhat voltage you are running at iddle and what voltage you are running while under full power.